【LeetCode】028. 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：

 1 class Solution {
 2 public:
 3     int strStr(string haystack, string needle) {
 4         int pos = -1;
 5         int len1 = haystack.size(), len2 = needle.size();
 6         for (int i = 0; i <= len1 - len2; ++i) {
 7             int p1 = i, p2 = 0;
 8             while (p1 < len1 && p2 < len2) {
 9                 if (haystack[p1] != needle[p2])
10                     break;
11                 ++p1;
12                 ++p2;
13             }
14             if (p2 == len2)
15                 return i;
16         }
17         return -1;
18     }
19 };