OMG 巨难

28. 找出字符串中第一个匹配项的下标

kmp,,很折磨

class Solution {
public:
    void getNext(int *next, const string &s)
    {
        int j = -1;
        next[0] = j;
        for (int i = 1; i < s.size(); i ++)
        {
            while (j >= 0 && s[i] != s[j+1])
            {
                j = next[j];
            }
            if (s[i] == s[j+1])
            {
                j ++;
            }
            next[i] = j;
        }
    }

    int strStr(string haystack, string needle) {
        if (needle.size() == 0) return 0;
        int next[needle.size()];
        getNext(next, needle);
        int j = -1;
        for (int i = 0; i < haystack.size(); i ++)
        {
            while (j >= 0 && needle[j+1] != haystack[i])
            {
                j = next[j];
            }
            if (haystack[i] == needle[j+1])
            {
                j ++;
            }
            if (j == needle.size() - 1)
            {
                return i - needle.size() + 1;
            }
        }
        return -1;
    }
};

459. 重复的子字符串

class Solution {
public:
    bool repeatedSubstringPattern(string s) {
        return (s+s).find(s,1) != s.size();
    }
};