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87 lines
1.3 KiB
Markdown
87 lines
1.3 KiB
Markdown
# [28. Implement strStr()](https://leetcode.com/problems/implement-strstr/)
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## 题目
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Implement strStr().
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Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
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**Example 1**:
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```
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Input: haystack = "hello", needle = "ll"
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Output: 2
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```
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**Example 2**:
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```
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Input: haystack = "aaaaa", needle = "bba"
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Output: -1
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```
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**Clarification**:
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What should we return when needle is an empty string? This is a great question to ask during an interview.
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For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().
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## 题目大意
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实现一个查找 substring 的函数。如果在母串中找到了子串，返回子串在母串中出现的下标，如果没有找到，返回 -1，如果子串是空串，则返回 0 。
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## 解题思路
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这一题比较简单，直接写即可。
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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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// 解法一
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func strStr(haystack string, needle string) int {
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for i := 0; ; i++ {
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for j := 0; ; j++ {
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if j == len(needle) {
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return i
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}
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if i+j == len(haystack) {
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return -1
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}
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if needle[j] != haystack[i+j] {
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break
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}
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}
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}
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}
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// 解法二
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func strStr1(haystack string, needle string) int {
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return strings.Index(haystack, needle)
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}
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```
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