Submission #124708

#	Time	Username	Problem	Language	Result	Execution time	Memory
124708		eriksuenderhauf	Kangaroo (CEOI16_kangaroo)	C++11	100 / 100	33 ms	23032 KiB

kangaroo

#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
#define mem(a,v) memset((a), (v), sizeof (a))
#define enl printf("\n")
#define case(t) printf("Case #%d: ", (t))
#define ni(n) scanf("%d", &(n))
#define nl(n) scanf("%I64d", &(n))
#define nai(a, n) for (int i = 0; i < (n); i++) ni(a[i])
#define nal(a, n) for (int i = 0; i < (n); i++) nl(a[i])
#define pri(n) printf("%d\n", (n))
#define prl(n) printf("%I64d\n", (n))
#define pii pair<int, int>
#define pil pair<int, long long>
#define pll pair<long long, long long>
#define vii vector<pii>
#define vil vector<pil>
#define vll vector<pll>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef cc_hash_table<ll,int,hash<ll>> ht;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> oset;
const double pi = acos(-1);
const int MOD = 1e9 + 7;
const int MOD2 = 1e9 + 9;
const int INF = 1e9 + 7;
const int MAXN = 2e3 + 5;
const double eps = 1e-9;
int n, cs, cf;
ll dp[MAXN][MAXN];

ll solve(int x, int y) {
	dp[n+1][0] = 1;
	int fl = 0;
	for (int i = n; i > 0; i--) {
		for (int j = 1; j <= n - i + 1; j++) {
			if (i == cs)
				dp[i][j] = dp[i+1][j-x];
			else if (i == cf)
				dp[i][j] = dp[i+1][j-y];
			else
				dp[i][j] = (dp[i+1][j-1] * 1ll * (ll) (j - fl) + dp[i+1][j+1] * 1ll * (ll) j) % MOD;
		}
		if (i == cs || i == cf)
			fl++;
	}
	return dp[1][1];
}

int main() {
	scanf("%d %d %d", &n, &cs, &cf);
	ll ans = (solve(0, (n+1)&1) + solve(1, n&1)) % MOD;
	printf("%lld\n", ans);
    return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:60:7: 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