【LeetCode】28. Implement strStr() 解题小结

题目：

Implement strStr().

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

简单题。

class Solution {
public:
    int strStr(string haystack, string needle) {
        if (needle.empty()) return 0;
        if (haystack.empty()) return -1;
        if (haystack.size() < needle.size()) return -1;

        int i, j;
        for (i = 0, j = 0; i+j < haystack.size(); ) {
            if (haystack[i+j] != needle[j]) {
                i++;
                j = 0;
            }
            else
                j++;
            if (j == needle.size()) return i;
        }
        return -1;
    }
};