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Submission #24761

# Submission time Handle Problem Language Result Execution time Memory
24761 2017-06-13T03:40:29 Z nibnalin Kangaroo (CEOI16_kangaroo) C++14
100 / 100
 156 ms 33456 KB 
#include <iostream>
#include <cstdio>
#include <vector>
using namespace std;

typedef long long int lli;

const lli maxn = lli(2e3)+5, MOD = lli(1e9)+7;

lli n, cs, cf, memo[maxn][maxn];

inline lli c2(lli x)
{
	return ((x*(x-1ll)))%MOD;
}

lli DP(lli idx, lli chains, lli start, lli end)
{
	if(idx == n) return (!start && !end && !chains);
	if(idx > cs && !start) return 0;
	if(idx > cf && !end) return 0;
	else if(memo[idx][chains] != -1) return memo[idx][chains]%MOD;
	else if(idx == cs)
	{
		lli res = DP(idx+1, chains, 1, end)%MOD;
		if(chains)
		{
			res += chains*DP(idx+1, chains-1, 1, end)%MOD;
			res %= MOD;
		}
		if(end)
		{
			res += DP(idx+1, chains, 0, 0)%MOD;
			res %= MOD;
		}
		res %= MOD;
		memo[idx][chains] = res;
		//cout << idx << " " << chains << " " << start << " " << end << ": " << res << "\n";
		return res;
	}
	else if(idx == cf)
	{
		lli res = DP(idx+1, chains, start, 1)%MOD;
		if(chains)
		{
			res += chains*DP(idx+1, chains-1, start, 1)%MOD;
			res %= MOD;
		}
		if(start)
		{
			res += DP(idx+1, chains, 0, 0)%MOD;
			res %= MOD;
		}
		res %= MOD;
		memo[idx][chains] = res;
		//cout << idx << " " << chains << " " << start << " " << end << ": " << res << "\n";
		return res;
	}
	else
	{
		lli res = DP(idx+1, chains+1, start, end)%MOD;
		if(chains > 1)
		{
			res += c2(chains)*DP(idx+1, chains-1, start, end)%MOD;
			res %= MOD;
		}
		if(start && chains)
		{
			res += chains*DP(idx+1, chains-1, start, end)%MOD;
			res %= MOD;
		}
		if(chains && end)
		{
			res += chains*DP(idx+1, chains-1, start, end)%MOD;
			res %= MOD;
		}
		if(start && end)
		{
			res += DP(idx+1, chains, start-1, end-1)%MOD;
			res %= MOD;
		}
		res %= MOD;
		memo[idx][chains] = res;
		//cout << idx << " " << chains << " " << start << " " << end << ": " << res << "\n";
		return res;
	}
}

int main(void)
{
	scanf("%lld%lld%lld", &n, &cs, &cf);
	cs--, cf--;

	for(lli i = 0;i <= n;i++)
	{
		for(lli j = 0;j <= n;j++)
		{
			memo[i][j] = -1;
		}
	}

	printf("%lld\n", DP(0, 0, 0, 0)%MOD);
}

Compilation message

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:91:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld%lld%lld", &n, &cs, &cf);
                                     ^

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 33424 KB Output is correct
2 Correct 0 ms 33424 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 33424 KB Output is correct
2 Correct 0 ms 33424 KB Output is correct
3 Correct 0 ms 33424 KB Output is correct
4 Correct 0 ms 33424 KB Output is correct
5 Correct 0 ms 33424 KB Output is correct
6 Correct 0 ms 33424 KB Output is correct
7 Correct 0 ms 33424 KB Output is correct
8 Correct 0 ms 33424 KB Output is correct
9 Correct 0 ms 33424 KB Output is correct
10 Correct 0 ms 33424 KB Output is correct
11 Correct 0 ms 33424 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 33424 KB Output is correct
2 Correct 0 ms 33424 KB Output is correct
3 Correct 0 ms 33424 KB Output is correct
4 Correct 0 ms 33424 KB Output is correct
5 Correct 0 ms 33424 KB Output is correct
6 Correct 0 ms 33424 KB Output is correct
7 Correct 0 ms 33424 KB Output is correct
8 Correct 0 ms 33424 KB Output is correct
9 Correct 0 ms 33424 KB Output is correct
10 Correct 0 ms 33424 KB Output is correct
11 Correct 0 ms 33424 KB Output is correct
12 Correct 0 ms 33424 KB Output is correct
13 Correct 0 ms 33424 KB Output is correct
14 Correct 0 ms 33424 KB Output is correct
15 Correct 0 ms 33424 KB Output is correct
16 Correct 0 ms 33424 KB Output is correct
17 Correct 0 ms 33424 KB Output is correct
18 Correct 0 ms 33424 KB Output is correct
19 Correct 0 ms 33424 KB Output is correct
20 Correct 0 ms 33424 KB Output is correct

Subtask #4
49.0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 33424 KB Output is correct
2 Correct 0 ms 33424 KB Output is correct
3 Correct 0 ms 33424 KB Output is correct
4 Correct 0 ms 33424 KB Output is correct
5 Correct 0 ms 33424 KB Output is correct
6 Correct 0 ms 33424 KB Output is correct
7 Correct 0 ms 33424 KB Output is correct
8 Correct 0 ms 33424 KB Output is correct
9 Correct 0 ms 33424 KB Output is correct
10 Correct 0 ms 33424 KB Output is correct
11 Correct 0 ms 33424 KB Output is correct
12 Correct 0 ms 33424 KB Output is correct
13 Correct 0 ms 33424 KB Output is correct
14 Correct 0 ms 33424 KB Output is correct
15 Correct 0 ms 33424 KB Output is correct
16 Correct 0 ms 33424 KB Output is correct
17 Correct 0 ms 33424 KB Output is correct
18 Correct 0 ms 33424 KB Output is correct
19 Correct 0 ms 33424 KB Output is correct
20 Correct 0 ms 33424 KB Output is correct
21 Correct 13 ms 33424 KB Output is correct
22 Correct 13 ms 33424 KB Output is correct
23 Correct 13 ms 33424 KB Output is correct
24 Correct 109 ms 33456 KB Output is correct
25 Correct 106 ms 33456 KB Output is correct
26 Correct 89 ms 33456 KB Output is correct
27 Correct 156 ms 33452 KB Output is correct
28 Correct 63 ms 33424 KB Output is correct