Submission #119956

#	Time	Username	Problem	Language	Result	Execution time	Memory
119956		arman_ferdous	Tents (JOI18_tents)	C++14	100 / 100	364 ms	71472 KiB

tents

#include <bits/stdc++.h>
using namespace std;

using ll = long long;
const int N = 3010;
const int MOD = 1e9+7;

ll n, m;
ll dp[N][N];

void add(ll &x, ll y) { x += y; if(x >= MOD) x -= MOD; }

ll DP(ll r, ll c) {
	if(r <= 0 || c <= 0) return 1;
	if(dp[r][c] != -1) return dp[r][c];
	dp[r][c] = DP(r - 1, c);
	add(dp[r][c], (4ll * c * DP(r - 1, c - 1) % MOD) );
	add(dp[r][c], (((c * (c - 1)) >> 1) * DP(r - 1, c - 2) % MOD) );
	add(dp[r][c], (c * (r - 1) * DP(r - 2, c - 1) % MOD) );

	return dp[r][c];
}

int main() {
	scanf("%lld %lld", &n, &m);
	memset(dp, -1, sizeof dp);
	printf("%lld\n", (DP(n, m) - 1 + MOD) % MOD);
	return 0;
}

Compilation message (stderr)

tents.cpp: In function 'int main()':
tents.cpp:25:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld %lld", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 48 / 48
• Subtask 2: 52 / 52