Theme Section---hdu4763(kmp, Next数组的运用)

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;

const int N = 1e6+7;

int Next[N];
char s[N], ss[N], sm[N];

void GetNext(char s[], int n)
{
    int i=0, j=-1;
    Next[0] = -1;
    while(i<n)
    {
        if(j==-1 || s[i]==s[j])
            Next[++i] = ++j;
        else
            j = Next[j];
    }
}
bool kmp(char a[], int n, char b[], int m)
{
    int i=0, j=0;
    while(i < m)
    {
        if(j==-1 || a[j] == b[i])
            i++,j++;
        else
            j = Next[j];
        if(j == n)
            return true;
    }
    return false;
}
int main()
{
    int n;
    scanf("%d", &n);
    for(int i=0; i<n; i++)
    {
        scanf("%s", s);
        int len = strlen(s);
        GetNext(s, len);
        int k = Next[len];
        while(k>len/3)k=Next[k];
        while(k>0)
        {
            memset(ss, 0,sizeof(ss));
            strncpy(ss, s, k);///一定不要忘记初始化；
            memset(sm, 0,sizeof(sm));
            strncpy(sm, s+k, len-2*k);
            if(kmp(ss, k, sm, len-2*k)==true)
                break;
            else
                k=Next[k];
        }
        printf("%d\n", k);
    }
    return 0;
}