Submission #164781

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
164781	2019-11-23T10:54:52 Z	ttnhuy313	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	84 ms	31992 KB

kangaroo

#include <bits/stdc++.h>

using namespace std;
#define int long long

const int N = 2005, MOD = 1e9 + 7;
int n, s, t, memo[N][N];

void add(int &a, int b) {
	a = (a + b) % MOD;
	return;
}

int calc(int pos, int k) {
	if (pos == n + 1)
		return (k == 1);
	if (~memo[pos][k]) return memo[pos][k];
	int ret = 0;
	if (pos == s) {
		add(ret,  calc(pos + 1, k));
		add(ret, calc(pos + 1, k + 1));
	} else if (pos == t) {
		add(ret, calc(pos + 1, k));
		add(ret, calc(pos + 1, k + 1));
	} else {
		add(ret, calc(pos + 1, k + 1) * (k + 1 - (pos > s) - (pos > t)));
		if (k >= 2) add(ret, calc(pos + 1, k - 1) * (k - 1));
	}
	return memo[pos][k] = ret;
}

main() {
	ios_base::sync_with_stdio(0); cin.tie(0);

	memset(memo, -1, sizeof memo);
	cin >> n >> s >> t;
	cout << calc(1, 0) << endl;

	return 0;
}

Compilation message

kangaroo.cpp:32:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main() {
      ^

Subtask #1

6.0 / 6.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	30 ms	31736 KB	Output is correct
2	Correct	30 ms	31740 KB	Output is correct

Subtask #2

30.0 / 30.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	30 ms	31736 KB	Output is correct
2	Correct	30 ms	31740 KB	Output is correct
3	Correct	31 ms	31736 KB	Output is correct
4	Correct	30 ms	31740 KB	Output is correct
5	Correct	30 ms	31864 KB	Output is correct
6	Correct	30 ms	31864 KB	Output is correct
7	Correct	30 ms	31864 KB	Output is correct
8	Correct	30 ms	31864 KB	Output is correct
9	Correct	31 ms	31720 KB	Output is correct
10	Correct	31 ms	31784 KB	Output is correct
11	Correct	34 ms	31736 KB	Output is correct

Subtask #3

15.0 / 15.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	30 ms	31736 KB	Output is correct
2	Correct	30 ms	31740 KB	Output is correct
3	Correct	31 ms	31736 KB	Output is correct
4	Correct	30 ms	31740 KB	Output is correct
5	Correct	30 ms	31864 KB	Output is correct
6	Correct	30 ms	31864 KB	Output is correct
7	Correct	30 ms	31864 KB	Output is correct
8	Correct	30 ms	31864 KB	Output is correct
9	Correct	31 ms	31720 KB	Output is correct
10	Correct	31 ms	31784 KB	Output is correct
11	Correct	34 ms	31736 KB	Output is correct
12	Correct	31 ms	31768 KB	Output is correct
13	Correct	31 ms	31864 KB	Output is correct
14	Correct	31 ms	31864 KB	Output is correct
15	Correct	31 ms	31864 KB	Output is correct
16	Correct	31 ms	31736 KB	Output is correct
17	Correct	31 ms	31864 KB	Output is correct
18	Correct	31 ms	31864 KB	Output is correct
19	Correct	31 ms	31864 KB	Output is correct
20	Correct	30 ms	31736 KB	Output is correct

Subtask #4

49.0 / 49.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	30 ms	31736 KB	Output is correct
2	Correct	30 ms	31740 KB	Output is correct
3	Correct	31 ms	31736 KB	Output is correct
4	Correct	30 ms	31740 KB	Output is correct
5	Correct	30 ms	31864 KB	Output is correct
6	Correct	30 ms	31864 KB	Output is correct
7	Correct	30 ms	31864 KB	Output is correct
8	Correct	30 ms	31864 KB	Output is correct
9	Correct	31 ms	31720 KB	Output is correct
10	Correct	31 ms	31784 KB	Output is correct
11	Correct	34 ms	31736 KB	Output is correct
12	Correct	31 ms	31768 KB	Output is correct
13	Correct	31 ms	31864 KB	Output is correct
14	Correct	31 ms	31864 KB	Output is correct
15	Correct	31 ms	31864 KB	Output is correct
16	Correct	31 ms	31736 KB	Output is correct
17	Correct	31 ms	31864 KB	Output is correct
18	Correct	31 ms	31864 KB	Output is correct
19	Correct	31 ms	31864 KB	Output is correct
20	Correct	30 ms	31736 KB	Output is correct
21	Correct	36 ms	31888 KB	Output is correct
22	Correct	36 ms	31864 KB	Output is correct
23	Correct	37 ms	31864 KB	Output is correct
24	Correct	80 ms	31964 KB	Output is correct
25	Correct	74 ms	31864 KB	Output is correct
26	Correct	73 ms	31864 KB	Output is correct
27	Correct	84 ms	31992 KB	Output is correct
28	Correct	67 ms	31864 KB	Output is correct