Submission #1257729

#	Time	Username	Problem	Language	Result	Execution time	Memory
1257729		trandangquang	Kangaroo (CEOI16_kangaroo)	C++20	100 / 100	15 ms	14920 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;

#define foru(i, a, b) for(int i = (a); i <= (b); ++i)
#define ford(i, a, b) for(int i = (a); i >= (b); --i)
#define rep(i, a) for(int i = 0; i < (a); ++i)
#define sz(a) (int)(a).size()
#define all(a) (a).begin(), (a).end()
#define bit(s, i) (((s) >> (i)) & 1)
#define ii pair <int, int>
#define fi first
#define se second
#define ll long long
#define eb emplace_back
#define pb push_back
#define __builtin_popcount __builtin_popcountll

template <class X, class Y>
    bool maxi(X &x, Y y) {
        if(x < y) {
            x = y;
            return true;
        }
        return false;
    }

template <class X, class Y>
    bool mini(X &x, Y y) {
        if(x > y) {
            x = y;
            return true;
        }
        return false;
    }

const int N=2222;
const int mod=1e9+7;

int n,cs,cf,dp[N][N];

inline int add(int a, int b){
    a+=b; if(a>=mod) a-=mod;
    return a;
}
inline int mul(int a, int b){
    return (ll)a*b % mod;
}

void solve(){
    cin>>n>>cs>>cf;

    dp[0][0]=1;
    foru(i,1,n){
        if(i==cs || i==cf){
            foru(j,1,i){
                dp[i][j]=add(dp[i][j],add(dp[i-1][j],dp[i-1][j-1]));
            }
        } else{
            foru(j,1,i){
                dp[i][j]=add(dp[i][j],mul(dp[i-1][j+1],j));
                int place = j-2+(i<cs)+(i<cf);
                if(j==1) place=1;
                dp[i][j]=add(dp[i][j],mul(dp[i-1][j-1],place));
            }
        }
    }
    cout<<dp[n][1]<<'\n';
}

int32_t main() {
    #define task "test"
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    cin.tie(0)->sync_with_stdio(0);

    int tc = 1; // cin >> tc;
    foru(i, 1, tc){
        solve();
    }
}

Compilation message (stderr)

kangaroo.cpp: In function 'int32_t main()':
kangaroo.cpp:73:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   73 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:74:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   74 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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