LeetCode: Implement strStr()

可以用c的方法

class Solution {
public:
    char *strStr(char *haystack, char *needle) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int haylen = strlen(haystack);
        int needlen = strlen(needle);
        for (int i = 0; i <= haylen-needlen; i++) {
            char *p = haystack + i;
            char *q = needle;
            while (*q != '\0' && *p == *q) {
                p++, q++;
            }
            if (*q == '\0') return haystack + i;
        }
        return NULL;
    }
};

再贴段更加清晰的代码

class Solution {
public:
    char *strStr(char *haystack, char *needle) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        string S, T;
        for (int i = 0; *(haystack+i) != '\0'; i++) S += *(haystack+i);
        for (int i = 0; *(needle+i) != '\0'; i++) T += *(needle+i);
        int m = S.size();
        int n = T.size();
        if (!n) return haystack;
        for (int i = 0; i < m-n+1; i++) {
            if (S.substr(i, n) == T) return haystack+i;
        }
        return NULL;
    }
};

public class Solution {
    public int StrStr(string haystack, string needle) {
        if (needle.Length == 0) return 0;
        for (int i = 0; i < haystack.Length - needle.Length + 1; i++) {
            if (haystack.Substring(i, needle.Length) == needle) return i;
        }
        return -1;
    }
}