Today I have done leetcode's June LeetCoding Challenge with cpp.

June LeetCoding Challenge 15

Description

Max Difference You Can Get From Changing an Integer

You are given an integer num. You will apply the following steps to num two separate times:

• Pick a digit x (0 <= x <= 9).
• Pick another digit y (0 <= y <= 9). Note y can be equal to x.
• Replace all the occurrences of x in the decimal representation of num by y.

Let a and b be the two results from applying the operation to num independently.

Return the max difference between a and b.

Note that neither a nor b may have any leading zeros, and must not be 0.

Example 1:

Input: num = 555
Output: 888
Explanation: The first time pick x = 5 and y = 9 and store the new integer in a.
The second time pick x = 5 and y = 1 and store the new integer in b.
We have now a = 999 and b = 111 and max difference = 888

Example 2:

Input: num = 9
Output: 8
Explanation: The first time pick x = 9 and y = 9 and store the new integer in a.
The second time pick x = 9 and y = 1 and store the new integer in b.
We have now a = 9 and b = 1 and max difference = 8

Constraints:

• 1 <= num <= 108

Solution

class Solution {
public:
  int maxDiff(int num) {
    string n = to_string(num);
    string maxN = n;
    int len = n.length();
    int start = 0;
    while(start < len && maxN[start] == '9') start += 1;
    for(int i = start + 1; i < len; ++i) {
      if(maxN[i] == maxN[start]) maxN[i] = '9';
    }
    if(start < len) maxN[start] = '9';

    string minN = n;
    bool changed = false;
    for(int i = 0; i < len && !changed; ++i) {
      char target = minN[i];
      if(!i) {
        if(target == '1') continue;
        changed = true;
        for(int j = 0; j < len; ++j) {
          if(minN[j] == target) minN[j] = '1';
        }
      } else {
        if(target == '0' || target == minN[0]) continue;
        changed = true;
        for(int j = 0; j < len; ++j) {
          if(minN[j] == target) minN[j] = '0';
        }
      }
    }
    return stoi(maxN) - stoi(minN);
  }
};

// Accepted
// 211/211 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 66.9 % of cpp submissions (8.2 MB)