KMP算法

待更新

例题

https://leetcode.cn/problems/find-the-index-of-the-first-occurrence-in-a-string/description/

class Solution {vector<int> next;void getNext(string s){int j=-1;next[0]=-1;int len=s.size();for(int i=1;i<len;i++){while(j!=-1 && s[i]!=s[j+1]){j=next[j];}if(s[i]==s[j+1]){j++;}next[i]=j;}}int KMP(string text,string pattern){int n=text.size(),m=pattern.size();next.clear();next.resize(m);getNext(pattern);int j=-1;for(int i=0;i<n;i++){while(j!=-1 && text[i]!=pattern[j+1]){j=next[j];}if(text[i]==pattern[j+1]){j++;}if(j==m-1){return i-m+1;}}return -1;}
public:int strStr(string haystack, string needle) {return KMP(haystack,needle);}
};