Given two strings A and B of lowercase letters, return true if and only if we can swap two letters in A so that the result equals B.

Example 1:

Input: A = "ab", B = "ba"Output: true

Example 2:

Input: A = "ab", B = "ab"Output: false

Example 3:

Input: A = "aa", B = "aa"Output: true

Example 4:

Input: A = "aaaaaaabc", B = "aaaaaaacb"Output: true

Example 5:

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

Note:

0 <= A.length <= 200000 <= B.length <= 20000A and B consist only of lowercase letters.

难度: Medium

题目：给定两字符串Ａ和Ｂ且由小写字线组成，返回ＡＢ是否由仅交换两个字符可以相互生成。

思路：判断长度，记录不同位置的个数，记录是否有相同的字符。

Runtime: 3 ms, faster than 81.94% of Java online submissions for Buddy Strings.

Memory Usage: 38.6 MB, less than 50.00% of Java online submissions for Buddy Strings.

class Solution {    public boolean buddyStrings(String A, String B) {        if (A.length() != B.length()) {            return false;        }                int[] tableA = new int[26];        int[] tableB = new int[26];        int diffPosition = 0;        for (int i = 0; i < A.length(); i++) {            char a = A.charAt(i);            char b = B.charAt(i);            if (a != b) {                diffPosition++;            }            if (diffPosition > 2) {                return false;            }            tableA[a - 'a']++;            tableB[b - 'a']++;        }                boolean duplicated = false;        for (int i = 0; !duplicated && i < 26; i++) {            if (tableA[i] != tableB[i]) {                return false;            }            duplicated = tableA[i] > 1 ? !duplicated : duplicated;        }                return 2 == diffPosition || duplicated;    }}