Hdu 3336(KMP+DP)

hdu 3336
如果$next[j] = i$, 那么说明$[0, i-1]$与$[j-i, j-1]$部分相同
并且$i,j$之间没有更多的前缀
设$dp[i]$为前$i$个字符中前缀出现次数
$dp[i] = dp[next[i]]+1 $

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
using namespace std;
#define ms(i,j) memset(i, j, sizeof i);

const int MAXN = 200000 + 5;

char s[MAXN];
int f[MAXN], dp[MAXN], n;

void init()
{
    scanf("%d", &n);
    scanf("%s", s);
}
void solve()
{
    f[0] = f[1] = 0;
    for (int i=1;i<n;i++)
    {
        int j = f[i];
        while (j && s[i]!=s[j]) j = f[j];
        f[i+1] = (s[i]==s[j]) ? (j+1) : (0); 
    }
    ms(dp, 0);
    int ans = 0;
    for (int i=1;i<=n;i++)
    {
        dp[i] = dp[f[i]] + 1; 
        ans = (ans+dp[i]) % 10007;
    }
    printf("%d\n", ans);
}
int main()
{
    int t;
    scanf("%d", &t); 
    while (t--)
    {
        init();
        solve();
    }
    return 0;
}