【LeetCode】028. 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

题解：

class Solution {
public:
    int strStr(string haystack, string needle) {
        int pos = -1;
        int len1 = haystack.size(), len2 = needle.size();
        for (int i = 0; i <= len1 - len2; ++i) {
            int p1 = i, p2 = 0;
            while (p1 < len1 && p2 < len2) {
                if (haystack[p1] != needle[p2])
                    break;
                ++p1;
                ++p2;
            }
            if (p2 == len2)
                return i;
        }
        return -1;
    }
};