28. Implement strStr()【easy】

28. Implement strStr()【easy】

Implement strStr().

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

解法一：

 class Solution {
 public:
     int strStr(string haystack, string needle) {
         if (haystack.empty() && needle.empty()) {
             return ;
         }

         if (haystack.empty()) {
             return -;
         }

         if (haystack.size() < needle.size()) {
             return -;
         }

         for (string::size_type i = ; i < haystack.size() - needle.size() + ; i++) {
             string::size_type j = ;
             for (j = ; j < needle.size(); j++) {
                 if (haystack[i + j] != needle[j]) {
                     break;
                 }
             }

             if (j == needle.size()) {
                 return i;
             }
         }

         return -;
     }
 };