Submission #109085

#	Time	Username	Problem	Language	Result	Execution time	Memory
109085		DystoriaX	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	187 ms	47600 KiB

kangaroo

#include <bits/stdc++.h>

using namespace std;

int n, cs, cf;
int dp[2010][2010][3];

const int MOD = 1e9 + 7;

int add(long long a, long long b){
	return (a + b) % MOD;
}

int mul(long long a, long long b){
	return (a * b) % MOD;
}

int main(){
	scanf("%d%d%d", &n, &cs, &cf);

	dp[0][0][0] = 1;

	for(int i = 1; i <= n; i++){
		for(int j = 0; j <= n; j++){
			for(int k = 0; k <= 2; k++){
				if(k > j) continue;

				int v = dp[i - 1][j][k];
				if(i != cf && i != cs){
					dp[i][j - 1][k] = add(dp[i][j - 1][k], mul(v, j - 1));
					dp[i][j + 1][k] = add(dp[i][j + 1][k], mul(v, j + 1 - k));
				} else if (k < 2) {
					dp[i][j][k + 1] = add(dp[i][j][k + 1], v);
					dp[i][j + 1][k + 1] = add(dp[i][j + 1][k + 1], v);
				}
			}
		}
	}

	printf("%d\n", dp[n][1][2]);

	return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:19:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d", &n, &cs, &cf);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 15 / 15
• Subtask 4: 49 / 49