标签：return goal charAt get Strings swap diff LeetCode Buddy
原题链接在这里：https://leetcode.com/problems/buddy-strings/
题目：
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
0and2in"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 * 104sandgoalconsist of lowercase letters.
题解：
If length is different, then it can't bu buddy strings, return false.
If s and goal are equal, then at least there should be duplciate chars to be swapped.
Otherwise, there could be only two difference and corresponding place could be swapped.
Time Complexity: O(m). m = s.length().
Space: O(m).
AC Java:
1 class Solution {
2 public boolean buddyStrings(String s, String goal) {
3 int m = s.length();
4 int n = goal.length();
5 if(m != n){
6 return false;
7 }
8
9 if(s.equals(goal)){
10 HashSet<Character> hs = new HashSet<>();
11 for(char c : s.toCharArray()){
12 hs.add(c);
13 }
14
15 return hs.size() != m;
16 }
17
18 List<Integer> diff = new ArrayList<>();
19 for(int i = 0; i < m; i++){
20 if(s.charAt(i) != goal.charAt(i)){
21 diff.add(i);
22 }
23 }
24
25 return diff.size() == 2 && s.charAt(diff.get(0)) == goal.charAt(diff.get(1)) && s.charAt(diff.get(1)) == goal.charAt(diff.get(0));
26 }
27 }
标签：return,goal,charAt,get,Strings,swap,diff,LeetCode,Buddy 来源： https://www.cnblogs.com/Dylan-Java-NYC/p/16632831.html
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