Count the string - HDU 3336（next+dp）

#include<stdio.h>
#include<string.h>

const int MAXN = 1e6+7;
const int oo = 1e9+7;
const int mod = 10007;

char s[MAXN];
int next[MAXN], dp[MAXN];

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];
    }
}

int main()
{
    int T, N, ans;

    scanf("%d", &T);

    while(T--)
    {
        scanf("%d%s", &N, s);

        GetNext(s, N);

        next[N+1] = -1;
        ans = dp[0] = 0;

        for(int i=1; i<=N; i++)
        {
            dp[i] = (dp[next[i]] + 1) % mod;
            ans = (ans+dp[i]) % mod;
        }

        printf("%d\n", ans);
    }

    return 0;
}