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  • README.md
  • src/main/kotlin
    • g0001_0100
    • g0101_0200
      • s0103_binary_tree_zigzag_level_order_traversal
      • s0104_maximum_depth_of_binary_tree
      • s0106_construct_binary_tree_from_inorder_and_postorder_traversal

6 files changed

+395
-11
lines changed

‎README.md‎

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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0104 |[Maximum Depth of Binary Tree](src/main/kotlin/g0101_0200/s0104_maximum_depth_of_binary_tree)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 236 | 83.39
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508509
#### Day 11 Containers and Libraries
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0100 |[Same Tree](src/main/kotlin/g0001_0100/s0100_same_tree)| Easy | Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 267 | 24.51
944946
| 0101 |[Symmetric Tree](src/main/kotlin/g0101_0200/s0101_symmetric_tree)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 290 | 26.98
945947
| 0199 |[Binary Tree Right Side View](src/main/kotlin/g0101_0200/s0199_binary_tree_right_side_view)| Medium | Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 194 | 92.89
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|-|-|-|-|-|-
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| 0094 |[Largest Rectangle in Histogram](src/main/kotlin/g0001_0100/s0094_binary_tree_inorder_traversal)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Stack | 269 | 38.80
10761078
| 0102 |[Binary Tree Level Order Traversal](src/main/kotlin/g0101_0200/s0102_binary_tree_level_order_traversal)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree | 355 | 29.37
1079+
| 0103 |[Binary Tree Zigzag Level Order Traversal](src/main/kotlin/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal)| Medium | Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree | 316 | 34.25
10771080
| 0543 |[Diameter of Binary Tree](src/main/kotlin/g0501_0600/s0543_diameter_of_binary_tree)| Easy | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree | 307 | 43.93
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| 0100 |[Same Tree](src/main/kotlin/g0001_0100/s0100_same_tree)| Easy | Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 267 | 24.51
10781082
| 0226 |[Invert Binary Tree](src/main/kotlin/g0201_0300/s0226_invert_binary_tree)| Easy | Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 233 | 54.90
1083+
| 0104 |[Maximum Depth of Binary Tree](src/main/kotlin/g0101_0200/s0104_maximum_depth_of_binary_tree)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 236 | 83.39
10791084
| 0124 |[Binary Tree Maximum Path Sum](src/main/kotlin/g0101_0200/s0124_binary_tree_maximum_path_sum)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree | 331 | 74.42
10801085
| 0098 |[Validate Binary Search Tree](src/main/kotlin/g0001_0100/s0098_validate_binary_search_tree)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree | 330 | 41.38
10811086
| 0236 |[Lowest Common Ancestor of a Binary Tree](src/main/kotlin/g0201_0300/s0236_lowest_common_ancestor_of_a_binary_tree)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree | 386 | 45.21
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0102 |[Binary Tree Level Order Traversal](src/main/kotlin/g0101_0200/s0102_binary_tree_level_order_traversal)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree | 355 | 29.37
1207+
| 0104 |[Maximum Depth of Binary Tree](src/main/kotlin/g0101_0200/s0104_maximum_depth_of_binary_tree)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 236 | 83.39
12021208
| 0101 |[Symmetric Tree](src/main/kotlin/g0101_0200/s0101_symmetric_tree)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 290 | 26.98
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#### Day 12 Tree
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0105 |[Construct Binary Tree from Preorder and Inorder Traversal](src/main/kotlin/g0101_0200/s0105_construct_binary_tree_from_preorder_and_inorder_traversal)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer | 370 | 58.31
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| 0103 |[Binary Tree Zigzag Level Order Traversal](src/main/kotlin/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal)| Medium | Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree | 316 | 34.25
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#### Day 16 Tree
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| 0124 |[Binary Tree Maximum Path Sum](src/main/kotlin/g0101_0200/s0124_binary_tree_maximum_path_sum)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree, Udemy_Tree_Stack_Queue | 331 | 74.42
14961503
| 0121 |[Best Time to Buy and Sell Stock](src/main/kotlin/g0101_0200/s0121_best_time_to_buy_and_sell_stock)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Data_Structure_I_Day_3_Array, Dynamic_Programming_I_Day_7, Level_1_Day_5_Greedy, Udemy_Arrays | 609 | 94.06
14971504
| 0114 |[Flatten Binary Tree to Linked List](src/main/kotlin/g0101_0200/s0114_flatten_binary_tree_to_linked_list)| Medium | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Linked_List, Udemy_Linked_List | 191 | 93.10
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| 0106 |[Construct Binary Tree from Inorder and Postorder Traversal](src/main/kotlin/g0101_0200/s0106_construct_binary_tree_from_inorder_and_postorder_traversal)| Medium | Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer | 358 | 61.29
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| 0105 |[Construct Binary Tree from Preorder and Inorder Traversal](src/main/kotlin/g0101_0200/s0105_construct_binary_tree_from_preorder_and_inorder_traversal)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer, Data_Structure_II_Day_15_Tree | 370 | 58.31
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| 0104 |[Maximum Depth of Binary Tree](src/main/kotlin/g0101_0200/s0104_maximum_depth_of_binary_tree)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Programming_Skills_I_Day_10_Linked_List_and_Tree, Udemy_Tree_Stack_Queue | 236 | 83.39
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| 0103 |[Binary Tree Zigzag Level Order Traversal](src/main/kotlin/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal)| Medium | Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_II_Day_15_Tree, Udemy_Tree_Stack_Queue | 316 | 34.25
14991509
| 0102 |[Binary Tree Level Order Traversal](src/main/kotlin/g0101_0200/s0102_binary_tree_level_order_traversal)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Level_1_Day_6_Tree, Udemy_Tree_Stack_Queue | 355 | 29.37
15001510
| 0101 |[Symmetric Tree](src/main/kotlin/g0101_0200/s0101_symmetric_tree)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Level_2_Day_15_Tree | 290 | 26.98
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| 0100 |[Same Tree](src/main/kotlin/g0001_0100/s0100_same_tree)| Easy | Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Level_2_Day_15_Tree, Udemy_Tree_Stack_Queue | 267 | 24.51
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| 0099 |[Recover Binary Search Tree](src/main/kotlin/g0001_0100/s0099_recover_binary_search_tree)| Medium | Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree | 492 | 39.39
15011513
| 0098 |[Validate Binary Search Tree](src/main/kotlin/g0001_0100/s0098_validate_binary_search_tree)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Data_Structure_I_Day_14_Tree, Level_1_Day_8_Binary_Search_Tree, Udemy_Tree_Stack_Queue | 330 | 41.38
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| 0097 |[Interleaving String](src/main/kotlin/g0001_0100/s0097_interleaving_string)| Medium | String, Dynamic_Programming | 240 | 57.50
15031515
| 0096 |[Unique Binary Search Trees](src/main/kotlin/g0001_0100/s0096_unique_binary_search_trees)| Medium | Top_100_Liked_Questions, Dynamic_Programming, Math, Tree, Binary_Tree, Binary_Search_Tree, Dynamic_Programming_I_Day_11 | 237 | 26.76
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| 0036 |[Valid Sudoku](src/main/kotlin/g0001_0100/s0036_valid_sudoku)| Medium | Top_Interview_Questions, Array, Hash_Table, Matrix, Data_Structure_I_Day_5_Array | 346 | 65.03
15641576
| 0035 |[Search Insert Position](src/main/kotlin/g0001_0100/s0035_search_insert_position)| Easy | Top_100_Liked_Questions, Array, Binary_Search, Algorithm_I_Day_1_Binary_Search, Binary_Search_I_Day_2 | 267 | 50.32
15651577
| 0034 |[Find First and Last Position of Element in Sorted Array](src/main/kotlin/g0001_0100/s0034_find_first_and_last_position_of_element_in_sorted_array)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Algorithm_II_Day_1_Binary_Search, Binary_Search_I_Day_5 | 228 | 83.38
1566-
| 0033 |[Search in Rotated Sorted Array](src/main/kotlin/g0001_0100/s0033_search_in_rotated_sorted_array)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Algorithm_II_Day_1_Binary_Search | 184 | 86.08
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| 0033 |[Search in Rotated Sorted Array](src/main/kotlin/g0001_0100/s0033_search_in_rotated_sorted_array)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Algorithm_II_Day_1_Binary_Search, Binary_Search_I_Day_11, Level_2_Day_8_Binary_Search, Udemy_Binary_Search | 184 | 86.08
15671579
| 0032 |[Longest Valid Parentheses](src/main/kotlin/g0001_0100/s0032_longest_valid_parentheses)| Hard | Top_100_Liked_Questions, String, Dynamic_Programming, Stack | 215 | 95.71
15681580
| 0031 |[Next Permutation](src/main/kotlin/g0001_0100/s0031_next_permutation)| Medium | Top_100_Liked_Questions, Array, Two_Pointers | 211 | 94.23
15691581
| 0030 |[Substring with Concatenation of All Words](src/main/kotlin/g0001_0100/s0030_substring_with_concatenation_of_all_words)| Hard | String, Hash_Table, Sliding_Window | 441 | 85.84
15701582
| 0029 |[Divide Two Integers](src/main/kotlin/g0001_0100/s0029_divide_two_integers)| Medium | Top_Interview_Questions, Math, Bit_Manipulation, Udemy_Bit_Manipulation | 281 | 31.67
15711583
| 0028 |[Find the Index of the First Occurrence in a String](src/main/kotlin/g0001_0100/s0028_implement_strstr)| Easy | Top_Interview_Questions, String, Two_Pointers, String_Matching, Programming_Skills_II_Day_1 | 257 | 32.35
15721584
| 0027 |[Remove Element](src/main/kotlin/g0001_0100/s0027_remove_element)| Easy | Array, Two_Pointers | 293 | 32.19
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| 0026 |[Remove Duplicates from Sorted Array](src/main/kotlin/g0001_0100/s0026_remove_duplicates_from_sorted_array)| Easy | Top_Interview_Questions, Array, Two_Pointers | 361 | 77.19
1574-
| 0025 |[Reverse Nodes in k-Group](src/main/kotlin/g0001_0100/s0025_reverse_nodes_in_k_group)| Hard | Top_100_Liked_Questions, Linked_List, Recursion, Data_Structure_II_Day_13_Linked_List | 194 | 87.72
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| 0026 |[Remove Duplicates from Sorted Array](src/main/kotlin/g0001_0100/s0026_remove_duplicates_from_sorted_array)| Easy | Top_Interview_Questions, Array, Two_Pointers, Udemy_Two_Pointers | 361 | 77.19
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| 0025 |[Reverse Nodes in k-Group](src/main/kotlin/g0001_0100/s0025_reverse_nodes_in_k_group)| Hard | Top_100_Liked_Questions, Linked_List, Recursion, Data_Structure_II_Day_13_Linked_List, Udemy_Linked_List | 194 | 87.72
15751587
| 0024 |[Swap Nodes in Pairs](src/main/kotlin/g0001_0100/s0024_swap_nodes_in_pairs)| Medium | Top_100_Liked_Questions, Linked_List, Recursion, Data_Structure_II_Day_12_Linked_List, Udemy_Linked_List | 149 | 99.39
15761588
| 0023 |[Merge k Sorted Lists](src/main/kotlin/g0001_0100/s0023_merge_k_sorted_lists)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Heap_Priority_Queue, Linked_List, Divide_and_Conquer, Merge_Sort | 323 | 75.14
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| 0022 |[Generate Parentheses](src/main/kotlin/g0001_0100/s0022_generate_parentheses)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Backtracking, Algorithm_II_Day_11_Recursion_Backtracking | 210 | 78.51
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| 0021 |[Merge Two Sorted Lists](src/main/kotlin/g0001_0100/s0021_merge_two_sorted_lists)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Data_Structure_I_Day_7_Linked_List, Algorithm_I_Day_10_Recursion_Backtracking | 148 | 99.90
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| 0020 |[Valid Parentheses](src/main/kotlin/g0001_0100/s0020_valid_parentheses)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, String, Stack, Data_Structure_I_Day_9_Stack_Queue | 196 | 71.08
1580-
| 0019 |[Remove Nth Node From End of List](src/main/kotlin/g0001_0100/s0019_remove_nth_node_from_end_of_list)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Two_Pointers, Linked_List, Algorithm_I_Day_5_Two_Pointers | 172 | 85.17
1589+
| 0022 |[Generate Parentheses](src/main/kotlin/g0001_0100/s0022_generate_parentheses)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Backtracking, Algorithm_II_Day_11_Recursion_Backtracking, Udemy_Backtracking/Recursion | 210 | 78.51
1590+
| 0021 |[Merge Two Sorted Lists](src/main/kotlin/g0001_0100/s0021_merge_two_sorted_lists)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Data_Structure_I_Day_7_Linked_List, Algorithm_I_Day_10_Recursion_Backtracking, Level_1_Day_3_Linked_List, Udemy_Linked_List | 148 | 99.90
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| 0020 |[Valid Parentheses](src/main/kotlin/g0001_0100/s0020_valid_parentheses)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, String, Stack, Data_Structure_I_Day_9_Stack_Queue, Udemy_Strings | 196 | 71.08
1592+
| 0019 |[Remove Nth Node From End of List](src/main/kotlin/g0001_0100/s0019_remove_nth_node_from_end_of_list)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Two_Pointers, Linked_List, Algorithm_I_Day_5_Two_Pointers, Level_2_Day_3_Linked_List | 172 | 85.17
15811593
| 0018 |[4Sum](src/main/kotlin/g0001_0100/s0018_4sum)| Medium | Array, Sorting, Two_Pointers | 467 | 81.25
1582-
| 0017 |[Letter Combinations of a Phone Number](src/main/kotlin/g0001_0100/s0017_letter_combinations_of_a_phone_number)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Backtracking, Algorithm_II_Day_11_Recursion_Backtracking | 132 | 100.00
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| 0016 |[3Sum Closest](src/main/kotlin/g0001_0100/s0016_3sum_closest)| Medium | Array, Sorting, Two_Pointers | 219 | 89.56
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| 0015 |[3Sum](src/main/kotlin/g0001_0100/s0015_3sum)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Data_Structure_II_Day_1_Array, Algorithm_II_Day_3_Two_Pointers | 1059 | 55.28
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| 0014 |[Longest Common Prefix](src/main/kotlin/g0001_0100/s0014_longest_common_prefix)| Easy | Top_Interview_Questions, String | 269 | 48.51
1594+
| 0017 |[Letter Combinations of a Phone Number](src/main/kotlin/g0001_0100/s0017_letter_combinations_of_a_phone_number)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Backtracking, Algorithm_II_Day_11_Recursion_Backtracking, Udemy_Backtracking/Recursion | 132 | 100.00
1595+
| 0016 |[3Sum Closest](src/main/kotlin/g0001_0100/s0016_3sum_closest)| Medium | Array, Sorting, Two_Pointers, Level_2_Day_14_Sliding_Window/Two_Pointer | 219 | 89.56
1596+
| 0015 |[3Sum](src/main/kotlin/g0001_0100/s0015_3sum)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Data_Structure_II_Day_1_Array, Algorithm_II_Day_3_Two_Pointers, Udemy_Two_Pointers | 1059 | 55.28
1597+
| 0014 |[Longest Common Prefix](src/main/kotlin/g0001_0100/s0014_longest_common_prefix)| Easy | Top_Interview_Questions, String, Level_2_Day_2_String, Udemy_Strings | 269 | 48.51
15861598
| 0013 |[Roman to Integer](src/main/kotlin/g0001_0100/s0013_roman_to_integer)| Easy | Top_Interview_Questions, String, Hash_Table, Math | 293 | 78.06
15871599
| 0012 |[Integer to Roman](src/main/kotlin/g0001_0100/s0012_integer_to_roman)| Medium | String, Hash_Table, Math | 300 | 72.89
15881600
| 0011 |[Container With Most Water](src/main/kotlin/g0001_0100/s0011_container_with_most_water)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Greedy, Two_Pointers, Algorithm_II_Day_4_Two_Pointers | 474 | 89.18

‎src/main/kotlin/g0001_0100/s0099_recover_binary_search_tree/readme.md‎

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[![](https://img.shields.io/github/stars/javadev/LeetCode-in-Kotlin?label=Stars&style=flat-square)](https://github.com/javadev/LeetCode-in-Kotlin)
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[![](https://img.shields.io/github/forks/javadev/LeetCode-in-Kotlin?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/javadev/LeetCode-in-Kotlin/fork)
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## 99\. Recover Binary Search Tree
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Medium
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You are given the `root` of a binary search tree (BST), where the values of **exactly** two nodes of the tree were swapped by mistake. _Recover the tree without changing its structure_.
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**Example 1:**
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![](https://assets.leetcode.com/uploads/2020/10/28/recover1.jpg)
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**Input:** root = [1,3,null,null,2]
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**Output:** [3,1,null,null,2]
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**Explanation:** 3 cannot be a left child of 1 because 3 > 1. Swapping 1 and 3 makes the BST valid.
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**Example 2:**
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![](https://assets.leetcode.com/uploads/2020/10/28/recover2.jpg)
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**Input:** root = [3,1,4,null,null,2]
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**Output:** [2,1,4,null,null,3]
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**Explanation:** 2 cannot be in the right subtree of 3 because 2 < 3. Swapping 2 and 3 makes the BST valid.
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**Constraints:**
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* The number of nodes in the tree is in the range `[2, 1000]`.
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* <code>-2<sup>31</sup> <= Node.val <= 2<sup>31</sup> - 1</code>
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**Follow up:** A solution using `O(n)` space is pretty straight-forward. Could you devise a constant `O(1)` space solution?
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## Solution
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```kotlin
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import com_github_leetcode.TreeNode
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/*
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* Example:
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* var ti = TreeNode(5)
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* var v = ti.`val`
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* Definition for a binary tree node.
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* class TreeNode(var `val`: Int) {
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* var left: TreeNode? = null
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* var right: TreeNode? = null
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* }
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*/
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class Solution {
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private var prev: TreeNode? = null
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private var first: TreeNode? = null
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private var second: TreeNode? = null
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fun recoverTree(root: TreeNode?) {
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evalSwappedNodes(root)
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val temp: Int = first!!.`val`
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first!!.`val` = second!!.`val`
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second!!.`val` = temp
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}
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private fun evalSwappedNodes(curr: TreeNode?) {
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if (curr == null) {
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return
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}
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evalSwappedNodes(curr.left)
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if (prev != null && prev!!.`val` > curr.`val`) {
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if (first == null) {
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first = prev
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}
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second = curr
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}
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prev = curr
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evalSwappedNodes(curr.right)
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}
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}
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```

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