hdu 4647 Another Graph Game（高效）

題目連結：hdu 4647 Another Graph Game

解題思路

P[i]維護的為字首取模M為i最早出現的位置。

代碼

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
const int maxn = ;

int N, M, P[maxn];

int main () {
    while (scanf("%d%d", &N, &M) == ) {
        int s = , x;
        memset(P, -, sizeof(P));
        P[] = ;

        int ans = ;
        for (int i = ; i <= N; i++) {
            scanf("%d", &x);
            s = ((s + x) % M + M) % M;
            if (P[s] == -) P[s] = i;
            ans = max(ans, i - P[s]);
        }
        printf("%d\n", ans);
    }
    return ;
}