LeetCode 28. Implement strStr()

题目描述:

Implement strStr().

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

实现查找子串函数. 使用双重循环.

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