leetcode-master/problems/0028.实现strStr().md

题目地址

https://leetcode-cn.com/problems/implement-strstr/

思路

C++代码

class Solution {
public:
    void preKmp(int* next, const string& s){
        next[0]=-1;
        int j=-1;
        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()];
        preKmp(next, needle);

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

笔者在先后在腾讯和百度从事技术研发多年，利用工作之余重刷leetcode，本文 GitHub：https://github.com/youngyangyang04/leetcode-master 已经收录，欢迎star，fork，共同学习，一起进步。