【leetcode】28-Implement strStr

problem

​​Implement strStr​​

code

class Solution {
public:
    int strStr(string haystack, string needle) {
        if(needle.size()==0) return 0;
        if( (haystack.size()==0) || (haystack.size()<needle.size()) ) return -1;
        int index = -1;
        size_t len = haystack.size() - needle.size();
        for(size_t i=0; i<len+1; i++)
        {
            if(haystack[i]!=needle[0]) continue;
            size_t j = 1;
            for( ; j<needle.size(); )
            {
                if(haystack[i+j]!=needle[j]) break;
                j++;
            }
            if(j==needle.size()) { index = i; break;}//
        }
        return index;
    }
};

View Code

注意，

１．需要考虑特殊情况以及异常点；

２．获取第一个的index，所以得到一个结果就直接退出外层循环；

 

参考

１．​​leetcode​​;

完