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Submission #406337

# Submission time Handle Problem Language Result Execution time Memory
406337 2021-05-17T12:00:43 Z AriaH Kangaroo (CEOI16_kangaroo) C++11
51 / 100
 90 ms 60600 KB 
/** I can do this all day **/

#pragma GCC optimize("O2")
#include <bits/stdc++.h>
using namespace std;

typedef long long                   ll;
typedef long double                 ld;
typedef pair<int,int>               pii;
typedef pair<ll,ll>                 pll;
#define all(x)                      (x).begin(),(x).end()
#define F                           first
#define S                           second
#define Mp                          make_pair
#define SZ(x)			    		(int)x.size()
#define fast_io                     ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io                     freopen("in.txt" , "r+" , stdin) ; freopen("out.txt" , "w+" , stdout);

const int N = 2e3 + 10;
const ll mod = 1e9 + 7;
const ll mod2 = 998244353;
const ll inf = 8e18;
const int LOG = 22;

ll pw(ll a , ll b, ll M)  { return (!b ? 1 : (b & 1 ? (a * pw(a * a % M, b / 2, M)) % M : pw(a * a % M, b / 2, M))); }

ll inv, dp[N][4][N];

inline ll C2(int x)
{
	return 1ll * x * (x - 1) / 2;
}

int main()
{
	inv = pw(2, mod - 2, mod);
	int n, s, f;
	scanf("%d%d%d", &n, &s, &f);
	dp[0][0][0] = 1;
	for(int i = 0; i < n; i ++)
	{
		for(int c = 0; c < 3; c ++)
		{
			for(int j = 0; j <= i * 2; j ++)
			{
				ll cu = dp[i][c][j];
				if(!cu)  continue;
				if(i + 1 == s || i + 1 == f)
				{
					/// match be ye C beshe
					if(c) dp[i + 1][c - 1][j] = (dp[i + 1][c - 1][j] + cu * c) % mod;
					/// match be ye sare masir
					if(j > 1) dp[i + 1][c + 1][j - 2] = (dp[i + 1][c + 1][j - 2] + cu * j) % mod;
					dp[i + 1][c + 1][j] = (dp[i + 1][c + 1][j] + cu) % mod;
				}
				else
				{
					/// match beshe be 2 ta C
					if(c > 1)
					{
						dp[i + 1][c - 2][j] = (dp[i + 1][c - 2][j] + cu * C2(c)) % mod;
					}
					/// match beshe be 2 ta masir
					if(j > 1)
					{
						dp[i + 1][c][j - 2] = (dp[i + 1][c][j - 2] + cu * j * (j - 2) / 2) % mod;
					}
					/// ye masir c ye j
					if(c > 0 && j > 1)
					{
						dp[i + 1][c][j - 2] = (dp[i + 1][c][j - 2] + cu * c * j) % mod;
					}
					dp[i + 1][c][j + 2] = (dp[i + 1][c][j + 2] + cu * inv) % mod;
				}
			}
		}
	}
	/*for(int i = 0; i <= n; i ++)
	{
		for(int c = 0; c < 3; c ++)
		{
			for(int j = 0; j <= i; j ++)
			{
				if(dp[i][c][j])
				{
					printf("i = %d c = %d j = %d dp = %lld\n", i, c, j, dp[i][c][j]);
				}
			}
		}
	}
	*/
	printf("%lld\n", dp[n][0][0]);
    return 0;
}

/** test corner cases(n = 1?) watch for overflow or minus indices **/

Compilation message

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:38:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   38 |  scanf("%d%d%d", &n, &s, &f);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 332 KB Output is correct
2 Correct 1 ms 332 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 332 KB Output is correct
2 Correct 1 ms 332 KB Output is correct
3 Correct 1 ms 332 KB Output is correct
4 Correct 1 ms 460 KB Output is correct
5 Correct 1 ms 460 KB Output is correct
6 Correct 1 ms 460 KB Output is correct
7 Correct 1 ms 436 KB Output is correct
8 Correct 1 ms 460 KB Output is correct
9 Correct 1 ms 460 KB Output is correct
10 Correct 1 ms 460 KB Output is correct
11 Correct 1 ms 460 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 332 KB Output is correct
2 Correct 1 ms 332 KB Output is correct
3 Correct 1 ms 332 KB Output is correct
4 Correct 1 ms 460 KB Output is correct
5 Correct 1 ms 460 KB Output is correct
6 Correct 1 ms 460 KB Output is correct
7 Correct 1 ms 436 KB Output is correct
8 Correct 1 ms 460 KB Output is correct
9 Correct 1 ms 460 KB Output is correct
10 Correct 1 ms 460 KB Output is correct
11 Correct 1 ms 460 KB Output is correct
12 Correct 2 ms 1996 KB Output is correct
13 Correct 3 ms 2124 KB Output is correct
14 Correct 2 ms 1356 KB Output is correct
15 Correct 2 ms 1740 KB Output is correct
16 Correct 3 ms 1964 KB Output is correct
17 Correct 2 ms 1868 KB Output is correct
18 Correct 2 ms 1356 KB Output is correct
19 Correct 3 ms 2124 KB Output is correct
20 Correct 2 ms 2124 KB Output is correct

Subtask #4
0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 332 KB Output is correct
2 Correct 1 ms 332 KB Output is correct
3 Correct 1 ms 332 KB Output is correct
4 Correct 1 ms 460 KB Output is correct
5 Correct 1 ms 460 KB Output is correct
6 Correct 1 ms 460 KB Output is correct
7 Correct 1 ms 436 KB Output is correct
8 Correct 1 ms 460 KB Output is correct
9 Correct 1 ms 460 KB Output is correct
10 Correct 1 ms 460 KB Output is correct
11 Correct 1 ms 460 KB Output is correct
12 Correct 2 ms 1996 KB Output is correct
13 Correct 3 ms 2124 KB Output is correct
14 Correct 2 ms 1356 KB Output is correct
15 Correct 2 ms 1740 KB Output is correct
16 Correct 3 ms 1964 KB Output is correct
17 Correct 2 ms 1868 KB Output is correct
18 Correct 2 ms 1356 KB Output is correct
19 Correct 3 ms 2124 KB Output is correct
20 Correct 2 ms 2124 KB Output is correct
21 Correct 11 ms 9076 KB Output is correct
22 Correct 12 ms 9560 KB Output is correct
23 Correct 14 ms 11212 KB Output is correct
24 Incorrect 90 ms 60600 KB Output isn't correct
25 Halted 0 ms 0 KB -