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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