Submission #899056

#	Time	Username	Problem	Language	Result	Execution time	Memory
899056		lovrot	Tents (JOI18_tents)	C++17	100 / 100	270 ms	71880 KiB

tents

#include <cstdio> 
#include <cstring> 

using namespace std;

typedef long long ll; 

const int N = 3010; 
const int MOD = 1e9 + 7;

inline int add(int a, int b) {
	if(a + b < MOD) return a + b;
	return a + b - MOD; 
}

inline int mult(int a, int b) {
	return (ll) a * b % MOD;
}

inline int pot(int a, int b) {
	int ret = 1;
	for(; b; b /= 2, a = mult(a, a))
		if(b & 1) ret = mult(ret, a);
	return ret;
}

inline int inv(int a) {
	return pot(a, MOD - 2);
}

int w, h;

int C[N][N], DP[N][N];

int choose(int a, int b) {
	if(a == b|| !b) return 1;
	if(C[a][b] != -1) return C[a][b];
	return C[a][b] = add(choose(a - 1, b), choose(a - 1, b - 1));
}

int dp(int n, int m) {
	if(!n || !m) return 1;
	if(DP[n][m] != -1) return DP[n][m]; 
	
	int a = 0, b = 0, c = 0, d = 0;
	a = dp(n - 1, m); 
	b = mult(mult(4, m), dp(n - 1, m - 1)); 
	if(m > 1) c = mult(choose(m, 2), dp(n - 1, m - 2));
	if(n > 1) d = mult(mult(m, n - 1), dp(n - 2, m - 1));
//	printf("%d %d %d %d %d %d\n", n, m, a, b, c, d);
	return DP[n][m] = add(a, add(b, add(c, d)));
}

int main() {
	memset(C, -1, sizeof(C));
	memset(DP, -1, sizeof(DP));

	scanf("%d%d", &h, &w); 
	printf("%d\n", add(MOD - 1, dp(h, w)));	
	return 0;
}

Compilation message (stderr)

tents.cpp: In function 'int main()':
tents.cpp:58:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   58 |  scanf("%d%d", &h, &w);
      |  ~~~~~^~~~~~~~~~~~~~~~

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