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().

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class Solution { public: int strStr(string haystack, string needle) { if(haystack==needle) return 0; int szh = haystack.size(); int szn = needle.size(); for(int i=0; i<szh; ++i){ if(i+szn-1>=szh) break; if(haystack.substr(i, szn)==needle) return i; } return -1; } };