[leetcode]28. Implement strStr()

题目链接:https://leetcode.com/problems/implement-strstr/

Implement strStr().

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

方法1：

class Solution { public: int strStr(string haystack,string needle) { int m=(int)haystack.length(); int n=(int)needle.length(); for(int i=0;i<=m-n;i++) { int j; for(j=0;j<n;j++) { if(haystack[i+j]!=needle[j]) break; } if(j==n) return i; } return -1; } };

方法2：

class Solution{ public: int strStr(string haystack,string neddle) { int m=haystack.length(); int n=neddle.length(); if(m<n) return -1; for(int i=0;i<=m-n;i++) { if(haystack.substr(i,n)==neddle) return i; } return -1; } };