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

July LeetCoding Challenge 3

Description

Buddy Strings

Given two strings s and goal, return true if you can swap two letters in s so the result is equal to goal, otherwise, return false.

Swapping letters is defined as taking two indices i and j (0-indexed) such that i != j and swapping the characters at s[i] and s[j].

• For example, swapping at indices 0 and 2 in "abcd" results in "cbad".

Example 1:

Input: s = "ab", goal = "ba"
Output: true
Explanation: You can swap s[0] = 'a' and s[1] = 'b' to get "ba", which is equal to goal.

Example 2:

Input: s = "ab", goal = "ab"
Output: false
Explanation: The only letters you can swap are s[0] = 'a' and s[1] = 'b', which results in "ba" != goal.

Example 3:

Input: s = "aa", goal = "aa"
Output: true
Explanation: You can swap s[0] = 'a' and s[1] = 'a' to get "aa", which is equal to goal.

Constraints:

• 1 <= s.length, goal.length <= 2 * 104
• s and goal consist of lowercase letters.

Solution

class Solution {
public:
  bool buddyStrings(string A, string B) {
    if(A.size() != B.size())return false;
    vector<int> cnt(128);
    int pos = -1;
    for(int i = 0; i < A.size(); ++i) {
      cnt[A[i]] ++;
      if(A[i] != B[i] && pos == -1) {
        pos = i;
      } else if (A[i] != B[i]) {
        char temp = A[i];
        A[i] = A[pos];
        A[pos] = temp;
        return A == B;
      }
    }
    return pos == -1 && *max_element(cnt.begin(), cnt.end()) > 1;
  }
};

// Accepted
// 34/34 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 52.51 % of cpp submissions (7 MB)