基础算法 KMP

#include<cstdio>
#include<cstring>
#define MAXN 1000000
using namespace std;
int next[MAXN+5];
char a[MAXN+5],b[MAXN+5];
void getnext(char *s)
{
    int len=strlen(s),i;
    next[0]=-1;
    for(i=1;i<len;i++)
    {
        int j=next[i-1];
        while(j!=-1&&s[j]!=s[i-1])
            j=next[j];
        next[i]=j+1;
    }
}
int kmp(char *s1,char *s2)
{
    int i,j,len1=strlen(s1),len2=strlen(s2);
    if(len1<len2)
        return -1;
    for(i=0,j=0;i<=len1;i++,j++)
    {
        if(j==len2)
            return i-j;
        if(i==len1)
            return -1;
        while(j!=-1&&s1[i]!=s2[j])
            j=next[j];
    }
    return -1;
}
int main()
{
    scanf("%s%s",a,b);
    getnext(b);
    int site=kmp(a,b);
    if(site!=-1)
        printf("yes\n%d\n",site);
    else
        printf("no\n");
}