Leetcode37: Implement strStr()

Implement strStr().

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

Update (2014-11-02):

The signature of the function had been updated to return the index instead of the pointer. If you still see your function signature returns a char
* or String, please click the reload button  to
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这道题要实现在haystack字符串里找到第一次出现needle的索引号。用暴力搜索实现起来相对较简单。

class Solution {
public:
    int strStr(string haystack, string needle) {
        int length_h = haystack.length();
        int length_n = needle.length();
        int step = length_h - length_n + 1;
        for(int i = 0; i < step; i++)
        {
            int j;
            for(j = 0; j < length_n; j++)
            {
                if(haystack[i+j] == needle[j])
                    continue;
                else
                    break;
            }
            if(j == length_n)
                return i;
        }
        return -1;
    }
};