kmp

kmp，next带优化

#include<iostream>
#include<bits/stdc++.h>
using namespace std;
void getnext(char p[],int next[]){
    next[0]=-1;
    int i=0,j=-1;
    int n=strlen(p);
    while(i<n-1){
        if(j==-1||p[i]==p[j]){
            i++;
            j++;
            if(p[i]!=p[j])
                next[i]=j;
            else
                next[i]=next[j];
        }
        else
            j=next[j];
    }
}
int kmp(char s[],char p[],int next[]){
    int i=0,j=0;
    int slen=strlen(s);
    int plen=strlen(p);
    getnext(p,next);
    while(i<slen&&j<plen){
        if(j==-1||s[i]==p[j]){
            i++;
            j++;
        }
        else
            j=next[j];
    }
    if(j==plen){
        return i-j+1;
    }
    else return -1;
}
int main(){
    char s[]="ababxbababcadfdsss";
    char p[]="ba";
    int next[20]={0};
    cout<<kmp(s,p,next)<<endl;
    //输出next
    for (int i = 0; i < strlen(p); ++i){
        printf("%d ",next[i]);
    }
}

 

来源：https://www.cnblogs.com/warmingtxdy/p/11855925.html