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1946. Largest Number After Mutating Substring

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Description

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 any 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) any 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 <= 105
• num consists of only digits 0-9.
• change.length == 10
• 0 <= change[d] <= 9

Solutions

Python3

class Solution:
    def maximumNumber(self, num: str, change: List[int]) -> str:
        find = False
        nums = list(num)
        for i, c in enumerate(num):
            if int(c) < change[int(c)]:
                nums[i] = str(change[int(c)])
                find = True
            elif find and int(c) == change[int(c)]:
                continue
            elif find:
                break
        return ''.join(nums)

Java

class Solution {
    public String maximumNumber(String num, int[] change) {
        boolean find = false;
        char[] nums = num.toCharArray();
        for (int i = 0; i < num.length(); ++i) {
            int c = num.charAt(i) - '0';
            if (c < change[c]) {
                nums[i] = (char) ('0' + change[c]);
                find = true;
            } else if (find && c == change[c]) {
                continue;
            } else if (find) {
                break;
            }
        }
        return new String(nums);
    }
}

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