Implement strStr()

来源：Leetcode

原帖：http://oj.leetcode.com/problems/implement-strstr/

题目：
Implement strStr(). Returns a pointer to the first occurrence of needle in haystack, or null if needle is not part of haystack.

代码：

 class Solution {  
 public:  
   int strStr(char *haystack, char *needle) {  
     if (!haystack || !needle) return -1;  
     char* h_start = haystack;  
     while (1) {  
       char *h = haystack, *n = needle;  
       while (*n && *h && *h == *n) {  
         h++; n++;  
       }  
       if (*n == '\0') return haystack - h_start; // match position  
       if (*h == '\0') return -1;  
       haystack++;  
     }  
   }  
 };  
   
 class Solution {  
   char *strStr(char *haystack, char *needle) {  
     if (!haystack || !needle) return NULL;  
     int lenHaystack = strlen(haystack);  
     int lenNeedle = strlen(needle);  
     int i, j;  
     for (i = 0; i <= lenHaystack - lenNeedle; ++i) {  
       for (j = 0; j < lenNeedle; ++j) {  
         if (haystack[i + j] != needle[j]) break;  
       }  
       if (j == lenNeedle) return haystack + i;  
     }  
     return NULL;  
   }  
 };