Intel Code Challenge Final Round (Div. 1 + Div. 2, Combined) F - Uniformly Branched Trees 无根树->有根树+dp

F - Uniformly Branched Trees

#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define PII pair<int, int>
#define PLI pair<LL, int>
#define ull unsigned long long
using namespace std;

const int N = 1e3 + ;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;

LL dp[N][][N], inv[N], f[N], finv[N], g[N][];
int n, d, mod;

void init() {
    inv[] = f[] = finv[] = ;
    for(int i = ; i < N; i++) inv[i] = (mod-mod/i)*inv[mod%i]%mod;
    for(int i = ; i < N; i++) f[i] = f[i-]*i%mod;
    for(int i = ; i < N; i++) finv[i] = finv[i-]*inv[i]%mod;
}

int main() {
    scanf("%d%d%d", &n, &d, &mod);
    init();
    for(int i = ; i <= n; i++) dp[][][i] = ;
    for(int i = ; i <= d; i++) g[][i] = ;
    for(int i = ; i <= n; i++) {
        for(int j = ; j <= d; j++) {
            for(int k = ; k < i; k++) {
                for(int l = ; l <= j && l*k <= i; l++) {
                    dp[i][j][k] = (dp[i][j][k] + 1ll*dp[i-l*k][j-l][k-]*g[k][l])%mod;
                }
            }
            for(int k = ; k <= n; k++) dp[i][j][k] = (dp[i][j][k]+dp[i][j][k-])%mod;
        }
        g[i][] = dp[i][d-][n];
        for(int j = ; j <= d; j++)
            g[i][j] = g[i][j-]*(dp[i][d-][n]+j-)%mod*inv[j]%mod;
    }
    LL ans = ;
    if(n <= ) ans = ;
    else ans = dp[n][d][n/];
    if(n >  && !(n&)) {
        ans = (ans + mod - dp[n/][d-][n/] * (dp[n/][d-][n/]-) /  % mod) % mod;
    }
    printf("%lld\n", ans);
    return ;
}

/*
*/