CheckIfOneStringSwapCanMakeStringsEqual.cpp

// Source : https://leetcode.com/problems/check-if-one-string-swap-can-make-strings-equal/
// Author : Hao Chen
// Date   : 2021-03-19

/***************************************************************************************************** 
 *
 * You are given two strings s1 and s2 of equal length. A string swap is an operation where you choose 
 * two indices in a string (not necessarily different) and swap the characters at these indices.
 * 
 * Return true if it is possible to make both strings equal by performing at most one string swap on 
 * exactly one of the strings. Otherwise, return false.
 * 
 * Example 1:
 * 
 * Input: s1 = "bank", s2 = "kanb"
 * Output: true
 * Explanation: For example, swap the first character with the last character of s2 to make "bank".
 * 
 * Example 2:
 * 
 * Input: s1 = "attack", s2 = "defend"
 * Output: false
 * Explanation: It is impossible to make them equal with one string swap.
 * 
 * Example 3:
 * 
 * Input: s1 = "kelb", s2 = "kelb"
 * Output: true
 * Explanation: The two strings are already equal, so no string swap operation is required.
 * 
 * Example 4:
 * 
 * Input: s1 = "abcd", s2 = "dcba"
 * Output: false
 * 
 * Constraints:
 * 
 * 	1 <= s1.length, s2.length <= 100
 * 	s1.length == s2.length
 * 	s1 and s2 consist of only lowercase English letters.
 ******************************************************************************************************/

class Solution {
public:
    bool areAlmostEqual(string s1, string s2) {
        int p[2]={0};
        int diff=0;
        for(int i=0; i<s1.size(); i++){
            if (s1[i] ==s2[i]) continue;
            if (diff < 2) p[diff] = i;
            diff++;
        }
        
        return (diff==0) || ( (diff == 2) && s1[p[0]] == s2[p[1]] && s1[p[1]] == s2[p[0]]);
    }
};