【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 = -;
         int len1 = haystack.size(), len2 = needle.size();
         for (int i = ; i <= len1 - len2; ++i) {
             int p1 = i, p2 = ;
             while (p1 < len1 && p2 < len2) {
                 if (haystack[p1] != needle[p2])
                     break;
                 ++p1;
                 ++p2;
             }
             if (p2 == len2)
                 return i;
         }
         return -;
     }
 };