28.implement-strstr

Statement

简体中文English

Metadata

• Link: 实现 strStr()
• Difficulty: Easy
• Tag: 双指针 字符串 字符串匹配

实现 strStr() 函数。

给你两个字符串 haystack 和 needle ，请你在 haystack 字符串中找出 needle 字符串出现的第一个位置（下标从 0 开始）。如果不存在，则返回  -1 。

 

说明：

当 needle 是空字符串时，我们应当返回什么值呢？这是一个在面试中很好的问题。

对于本题而言，当 needle 是空字符串时我们应当返回 0 。这与 C 语言的 strstr() 以及 Java 的 indexOf() 定义相符。

 

示例 1：

输入：haystack = "hello", needle = "ll"
输出：2

示例 2：

输入：haystack = "aaaaa", needle = "bba"
输出：-1

示例 3：

输入：haystack = "", needle = ""
输出：0

 

提示：

• 0 <= haystack.length, needle.length <= 5 * 104
• haystack 和 needle 仅由小写英文字符组成

Metadata

• Link: Implement strStr()
• Difficulty: Easy
• Tag: Two Pointers String String Matching

Implement strStr().

Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Clarification:

What should we return when needle is an empty string? This is a great question to ask during an interview.

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().

 

Example 1:

Input: haystack = "hello", needle = "ll"
Output: 2

Example 2:

Input: haystack = "aaaaa", needle = "bba"
Output: -1

Example 3:

Input: haystack = "", needle = ""
Output: 0

 

Constraints:

• 0 <= haystack.length, needle.length <= 5 * 104
• haystack and needle consist of only lower-case English characters.

Solution

Python 3

class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        return haystack.find(needle)

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最后更新: October 11, 2023