LeetCode: Implement strStr()

可以用c的方法

 1 class Solution {

 2 public:

 3     char *strStr(char *haystack, char *needle) {

 4         // IMPORTANT: Please reset any member data you declared, as

 5         // the same Solution instance will be reused for each test case.

 6         int haylen = strlen(haystack);

 7         int needlen = strlen(needle);

 8         for (int i = 0; i <= haylen-needlen; i++) {

 9             char *p = haystack + i;

10             char *q = needle;

11             while (*q != '\0' && *p == *q) {

12                 p++, q++;

13             }

14             if (*q == '\0') return haystack + i;

15         }

16         return NULL;

17     }

18 };

 

再贴段更加清晰的代码

 1 class Solution {

 2 public:

 3     char *strStr(char *haystack, char *needle) {

 4         // Start typing your C/C++ solution below

 5         // DO NOT write int main() function

 6         string S, T;

 7         for (int i = 0; *(haystack+i) != '\0'; i++) S += *(haystack+i);

 8         for (int i = 0; *(needle+i) != '\0'; i++) T += *(needle+i);

 9         int m = S.size();

10         int n = T.size();

11         if (!n) return haystack;

12         for (int i = 0; i < m-n+1; i++) {

13             if (S.substr(i, n) == T) return haystack+i;

14         }

15         return NULL;

16     }

17 };

 

1 public class Solution {

2     public int StrStr(string haystack, string needle) {

3         if (needle.Length == 0) return 0;

4         for (int i = 0; i < haystack.Length - needle.Length + 1; i++) {

5             if (haystack.Substring(i, needle.Length) == needle) return i;

6         }

7         return -1;

8     }

9 }

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