g1801_1900.s1830_minimum_number_of_operations_to_make_string_sorted

Class Solution

java.lang.Object

g1801_1900.s1830_minimum_number_of_operations_to_make_string_sorted.Solution

public class Solution
extends Object

1830 - Minimum Number of Operations to Make String Sorted.

Hard

You are given a string s ( 0-indexed ). You are asked to perform the following operation on s until you get a sorted string:

1. Find the largest index i such that 1 <= i < s.length and s[i] < s[i - 1].
2. Find the largest index j such that i <= j < s.length and s[k] < s[i - 1] for all the possible values of k in the range [i, j] inclusive.
3. Swap the two characters at indices i - 1 and j.
4. Reverse the suffix starting at index i.

Return the number of operations needed to make the string sorted. Since the answer can be too large, return it modulo 109 + 7.

Example 1:

Input: s = “cba”

Output: 5

Explanation: The simulation goes as follows: Operation 1: i=2, j=2. Swap s[1] and s[2] to get s=“cab”, then reverse the suffix starting at 2. Now, s=“cab”.

Operation 2: i=1, j=2. Swap s[0] and s[2] to get s=“bac”, then reverse the suffix starting at 1. Now, s=“bca”.

Operation 3: i=2, j=2. Swap s[1] and s[2] to get s=“bac”, then reverse the suffix starting at 2. Now, s=“bac”.

Operation 4: i=1, j=1. Swap s[0] and s[1] to get s=“abc”, then reverse the suffix starting at 1. Now, s=“acb”.

Operation 5: i=2, j=2. Swap s[1] and s[2] to get s=“abc”, then reverse the suffix starting at 2. Now, s=“abc”.

Example 2:

Input: s = “aabaa”

Output: 2

Explanation: The simulation goes as follows:

Operation 1: i=3, j=4. Swap s[2] and s[4] to get s=“aaaab”, then reverse the substring starting at 3. Now, s=“aaaba”.

Operation 2: i=4, j=4. Swap s[3] and s[4] to get s=“aaaab”, then reverse the substring starting at 4. Now, s=“aaaab”.

Constraints:

• 1 <= s.length <= 3000
• s consists only of lowercase English letters.

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	makeStringSorted(String s)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

makeStringSorted

public int makeStringSorted(String s)