LeetCode-in-Java
1946. Largest Number After Mutating Substring
Medium
You are given a string num, which represents a large integer. You are also given a 0-indexed integer array change of length 10 that maps each digit 0-9 to another digit. More formally, digit d maps to digit change[d].
You may choose to mutate a single substring of num. To mutate a substring, replace each digit num[i] with the digit it maps to in change (i.e. replace num[i] with change[num[i]]).
Return a string representing the largest possible integer after mutating (or choosing not to) a single substring of num.
A substring is a contiguous sequence of characters within the string.
Example 1:
Input: num = “132”, change = [9,8,5,0,3,6,4,2,6,8]
Output: “832”
Explanation: Replace the substring “1”:
- 1 maps to change[1] = 8. Thus, “132” becomes “832”.
“832” is the largest number that can be created, so return it.
Example 2:
Input: num = “021”, change = [9,4,3,5,7,2,1,9,0,6]
Output: “934”
Explanation: Replace the substring “021”:
-
0 maps to change[0] = 9.
-
2 maps to change[2] = 3.
-
1 maps to change[1] = 4.
Thus, “021” becomes “934”.
“934” is the largest number that can be created, so return it.
Example 3:
Input: num = “5”, change = [1,4,7,5,3,2,5,6,9,4]
Output: “5”
Explanation: “5” is already the largest number that can be created, so return it.
Constraints:
1 <= num.length <= 105numconsists of only digits0-9.change.length == 100 <= change[d] <= 9
Solution
public class Solution {
public String maximumNumber(String num, int[] change) {
int n = num.length();
char[] nums = num.toCharArray();
char[] arr = new char[n];
for (int i = 0; i < n; i++) {
int val = nums[i] - '0';
arr[i] = (char) (change[val] + '0');
}
boolean flag = false;
for (int i = 0; i < n; i++) {
if (nums[i] < arr[i]) {
nums[i] = arr[i];
flag = true;
} else if (flag && nums[i] > arr[i]) {
break;
}
}
return String.valueOf(nums);
}
}