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 change1 = 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 change0 = 9.

• 2 maps to change2 = 3.

• 1 maps to change1 = 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:

• <code>1 <= num.length <= 10⁵</code>

• num consists of only digits 0-9.

• change.length == 10

• 0 <= change[d] <= 9