leetcode 28

28. Implement strStr()

Implement strStr().

Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

子串匹配问题，KMP忘了个干净~~  费了点劲终于完成了。

个人感觉是比较乱，对边界把握还是不准，提交了很多次才通过。

代码如下：

class Solution {
public:
    int strStr(string haystack, string needle) {
        if(haystack.length() == 0 || needle.length() == 0 || haystack.length() < needle.length())
        {
            if(haystack.length() == 0 && needle.length() == 0)
            {
                return 0;
            }
            if(haystack.length() != 0 && needle.length() == 0)
            {
                return 0;
            }
            return -1;
        }
        int n = haystack.length();
        int m = needle.length();
        int index = 0;
        int j=0;
        for(int i=0; i<n; i++)
        {
             if(haystack[i] == needle[j])
             {
                 j++;
                 index = i;
                 if(j == m)
                 {
                    return index-m+1;
                 }
             }
             else
             {
                 i = i -j;
                 j=0;
             }
             
        }
        return -1;
    }
};

100%~有点不科学~~~~