Leetcode2566. Maximum Difference by Remapping a Digit

Problem

You are given an integer num. Bob will sneakily remap one of the 10 possible digits(0 to 9) to another digit.

Return the difference between the maximum and minimum value Bob can make by remap exactly one digit in num.

Bob can remap a digit to it self.(not change)

Resulting number after remapping can contain leading zeros.

Intuition

Consider the number 11891, Bob can remap 1 to 9 to obtain the max 99899, and remap 1 to 0 to obtain the min 00890.

Consider the number 99919, Bob can remap 1 to 9 to obtain the max 99999, and remap 9 to 0 to obtain the min 00010.

Hence we can observe that remap the first non-9 digit to 9 to yield the max value. And replace the first digit to 0 to yield the min value.

COOOOOOOOOOOOODING

class Solution{
    public:
        int minMaxDifference(int num){
            string s = to_string(num);
            int i = 0;
            while(s[i] == '9' && i < s.length()-1) i+=1;

            string max = s;
            for(char& ch:max) if(ch==s[i]) ch='9';
            
            string min = s;
            for(char& ch:min) if(ch==s[0]) ch='0';
            return stoi(max)-stoi(mn);
        }
}