LeetCode-28. Implement strStr()

LeetCode-28. Implement strStr()

Implement strStr().

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

Example 1:

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

Example 2:

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

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()​​.

题解：

很多测试用例没说清楚

class Solution {public: int strStr(string haystack, string needle) { if (needle.size() == 0) { return 0; } if (haystack.size() < needle.size()) { return -1; } int res = -1; for (int i = 0; i <= haystack.size() - needle.size(); i++) { int k = i; for (int j = 0; j < needle.size(); j++) { if (haystack[k] != needle[j]) { break; } else { k++; } if (j == needle.size() - 1) { if (res == -1) { res = i; } else { res = min(res, i); } } } } return res; }};

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