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73 lines
1.9 KiB
Markdown
73 lines
1.9 KiB
Markdown
# [1624. Largest Substring Between Two Equal Characters](https://leetcode.com/problems/largest-substring-between-two-equal-characters/)
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## 题目
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Given a string `s`, return *the length of the longest substring between two equal characters, excluding the two characters.* If there is no such substring return `-1`.
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A **substring** is a contiguous sequence of characters within a string.
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**Example 1:**
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```
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Input: s = "aa"
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Output: 0
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Explanation: The optimal substring here is an empty substring between the two 'a's.
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```
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**Example 2:**
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```
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Input: s = "abca"
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Output: 2
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Explanation: The optimal substring here is "bc".
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```
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**Example 3:**
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```
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Input: s = "cbzxy"
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Output: -1
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Explanation: There are no characters that appear twice in s.
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```
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**Example 4:**
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```
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Input: s = "cabbac"
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Output: 4
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Explanation: The optimal substring here is "abba". Other non-optimal substrings include "bb" and "".
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```
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**Constraints:**
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- `1 <= s.length <= 300`
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- `s` contains only lowercase English letters.
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## 题目大意
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给你一个字符串 s，请你返回 两个相同字符之间的最长子字符串的长度 ，计算长度时不含这两个字符。如果不存在这样的子字符串，返回 -1 。子字符串 是字符串中的一个连续字符序列。
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## 解题思路
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- 简单题。取每个字符，扫描一次字符串，如果在字符串中还能找到相同的字符，则返回最末尾的那个字符，计算这两个字符之间的距离。取最末尾的字符是为了让两个相同的字符距离最长。扫描字符串过程中动态维护最长长度。如果字符串中不存在 2 个相同的字符，则返回 -1 。
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## 代码
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```go
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package leetcode
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import "strings"
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func maxLengthBetweenEqualCharacters(s string) int {
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res := -1
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for k, v := range s {
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tmp := strings.LastIndex(s, string(v))
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if tmp > 0 {
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if res < tmp-k-1 {
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res = tmp - k - 1
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}
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}
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}
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return res
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}
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``` |