buddy-strings.js

// 859. Buddy Strings
// Given two strings A and B of lowercase letters,
// return true if you can swap two letters in A so the result is equal to B, 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 A[i] and A[j]. 
// For example, swapping at indices 0 and 2 in "abcd" results in "cbad".

// Example 1:

// Input: A = "ab", B = "ba"
// Output: true
// Explanation: You can swap A[0] = 'a' and A[1] = 'b' to get "ba", which is equal to B.
// Example 2:

// Input: A = "ab", B = "ab"
// Output: false
// Explanation: The only letters you can swap are A[0] = 'a' and A[1] = 'b', which results in "ba" != B.
// Example 3:

// Input: A = "aa", B = "aa"
// Output: true
// Explanation: You can swap A[0] = 'a' and A[1] = 'a' to get "aa", which is equal to B.
// Example 4:

// Input: A = "aaaaaaabc", B = "aaaaaaacb"
// Output: true
// Example 5:

// Input: A = "", B = "aa"
// Output: false
 
// Constraints:

// 0 <= A.length <= 20000
// 0 <= B.length <= 20000
// A and B consist of lowercase letters.

/**
 * @param {string} A
 * @param {string} B
 * @return {boolean}
 */
var buddyStrings = function(A, B) {
    let diff = []
    if(A.length != B.length) return false
    if(A === B && new Set(A).size < A.length) return true
    for(let i = 0; i < A.length; i++ ){
        if(A[i] != B[i]){
            diff.push([A[i],B[i]])
        }
    }
    let first = diff[0]
    let last = diff[diff.length - 1]
    if(diff.length == 2 && first[0] == last[1] && first[1] == last[0]) return true
    return false
};