Submission #369125

#	Time	Username	Problem	Language	Result	Execution time	Memory
369125		Sparky_09	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	39 ms	31724 KiB

kangaroo

#include "bits/stdc++.h"
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define trav(a, x) for(auto& a : x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<ll, ll> pii;
typedef vector<ll> vi;
typedef vector<pii> vpi;

int rd() {
	int result = 0;
	char ch;
	ch = getchar();
	while(ch < '0' || ch > '9') ch = getchar();
	result = ch-'0';
	while (true) {
		ch = getchar();
		if (ch < '0' || ch > '9') break;
		result = result*10 + (ch - '0');
	}
	return result;
}

template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }

void usaco(string s){
  freopen((s+".in").c_str(), "r", stdin);
  freopen((s+".out").c_str(), "w", stdout);
}
const int mod = 1e9+7;

int n, a, b;
inline int add(int a, int b){
    return (a + b) % mod;
}
ll mul(ll a, ll b){
    return (a * b) % mod;
}
ll dp[2002][2002];

int main() {
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);
#ifdef LOCAL_DEFINE
	freopen("input.txt", "r", stdin);
#endif
	//connected components dp hard for me ;_;  
    cin >> n >> a >> b;
    dp[1][1] = 1;
    for(int i = 2; i <= n; ++i)
        for(int j = 1; j <= n; ++j){
            if(i == a or i == b)
                dp[i][j] = add(dp[i-1][j-1], dp[i-1][j]);
            else
                dp[i][j] = add(mul(dp[i-1][j+1], j), mul(dp[i-1][j-1], j - (i > a) - (i > b)));
        }
    cout << dp[n][1];
}

Compilation message (stderr)

kangaroo.cpp: In function 'void usaco(std::string)':
kangaroo.cpp:30:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   30 |   freopen((s+".in").c_str(), "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:31:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   31 |   freopen((s+".out").c_str(), "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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