Submission #26393

#	Time	Username	Problem	Language	Result	Execution time	Memory
26393		WhipppedCream	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	99 ms	17724 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
#define X first
#define Y second
#define pb push_back
#define mp make_pair
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector< ii > vii;
typedef long long L;
typedef vector< L > vL;
typedef vector< vL > vvL;
typedef vector< vi > vvi;
typedef vector< vii > vvii;
const int inf = 1e9;
const L inf8 = 1e18;
const int md = 1e9 + 7;
int s, e;
int dp[2005][2005];
void add(int &a, int b)
{
	a += b;
	if(a>= md) a -= md;
}
int mul(int a, int b)
{
	return (1LL*a*b)%md;
}
int cc(int i, int j)
{
	if(i>= s) j--;
	if(i>= e) j--;
	return j;
}
int main()
{
	int n; scanf("%d %d %d", &n, &s, &e);
	dp[0][0] = 1;
	int ans = 0;
	for(int i = 1; i<= n; i++)
	{
		for(int j = 0; j<= n; j++)
		{
			int v = dp[i-1][j];
			int f = cc(i-1, j);
			if(i == s)
			{
				add(dp[i][j], mul(f, v));
				add(dp[i][j+1], v);
				if(i == n && j == 1) add(ans, v);
			}
			else if(i == e)
			{
				add(dp[i][j], mul(f, v));
				add(dp[i][j+1], v);
				if(i == n && j == 1) add(ans, v);
			}
			else
			{
				add(dp[i][j+1], v);
				if(j && i-1>= s) add(dp[i][j-1], mul(f, v));
				if(j && i-1>= e) add(dp[i][j-1], mul(f, v));
				if(j) add(dp[i][j-1], mul(f, mul(f-1, v)));
				if(i == n && j == 2) add(ans, v);
			}
		}
	}
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:37:38: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int n; scanf("%d %d %d", &n, &s, &e);
                                      ^

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