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87 lines
2.3 KiB
Markdown
87 lines
2.3 KiB
Markdown
# [859. Buddy Strings](https://leetcode.com/problems/buddy-strings/)
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## 题目
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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.
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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].
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For example, swapping at indices 0 and 2 in "abcd" results in "cbad".
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**Example 1**:
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Input: s = "ab", goal = "ba"
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Output: true
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Explanation: You can swap s[0] = 'a' and s[1] = 'b' to get "ba", which is equal to goal.
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**Example 2**:
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Input: s = "ab", goal = "ab"
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Output: false
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Explanation: The only letters you can swap are s[0] = 'a' and s[1] = 'b', which results in "ba" != goal.
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**Example 3**:
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Input: s = "aa", goal = "aa"
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Output: true
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Explanation: You can swap s[0] = 'a' and s[1] = 'a' to get "aa", which is equal to goal.
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**Example 4**:
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Input: s = "aaaaaaabc", goal = "aaaaaaacb"
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Output: true
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**Constraints:**
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- 1 <= s.length, goal.length <= 2 * 10000
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- s and goal consist of lowercase letters.
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## 题目大意
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给你两个字符串 s 和 goal ，只要我们可以通过交换 s 中的两个字母得到与 goal 相等的结果，就返回 true；否则返回 false 。
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交换字母的定义是：取两个下标 i 和 j （下标从 0 开始）且满足 i != j ，接着交换 s[i] 和 s[j] 处的字符。
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例如，在 "abcd" 中交换下标 0 和下标 2 的元素可以生成 "cbad" 。
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## 解题思路
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分为两种情况进行比较:
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- s 等于 goal, s 中有重复元素就返回 true,否则返回 false
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- s 不等于 goal, s 中有两个下标不同的字符与 goal 中对应下标的字符分别相等
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## 代码
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```go
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package leetcode
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func buddyStrings(s string, goal string) bool {
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if len(s) != len(goal) || len(s) <= 1 {
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return false
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}
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mp := make(map[byte]int)
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if s == goal {
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for i := 0; i < len(s); i++ {
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if _, ok := mp[s[i]]; ok {
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return true
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}
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mp[s[i]]++
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}
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return false
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}
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first, second := -1, -1
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for i := 0; i < len(s); i++ {
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if s[i] != goal[i] {
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if first == -1 {
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first = i
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} else if second == -1 {
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second = i
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} else {
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return false
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}
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}
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}
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return second != -1 && s[first] == goal[second] && s[second] == goal[first]
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}
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``` |