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51 lines
914 B
Markdown
51 lines
914 B
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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```c
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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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```c
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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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