Submission #443377

#	Time	Username	Problem	Language	Result	Execution time	Memory
443377		1e18	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	51 ms	15900 KiB

kangaroo

#define _CRT_SECURE_NO_WARNINGS
#include <random>
#include <limits>
#include <assert.h>
#include <time.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vector>
#include <utility>
#include <algorithm>
#include <iterator>
#include <numeric>
#include <string>
#include <set>
#include <map>
using namespace std;
#define forn(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
#define mp make_pair
#define mt make_tuple
#define ff first
#define ss second
#define whats(a) cerr<<#a<<" "<<a<<endl;
#define Mod(a,b) (((a)%(b)+(b))%(b))
#define sz(x) (int((x).size()))
typedef long long ll;
typedef int Int;
//#define int ll

typedef vector<int> vec;
typedef vector<vec> mat;

const int N = 2000;
const int MOD = 1e9 + 7;

int dp[N + 1][N + 1];

void cadd(int& a, int b) {
    a += b;
    if (a >= MOD)a -= MOD;
}

int mul(ll a, int b) {
    return (a * b) % MOD;
}

Int main(Int argc, char* argv[])
{
#ifdef Home
    freopen("inp.txt", "rb", stdin);
#endif
    ios::sync_with_stdio(0);

    int n, cs, cf;
    cin >> n >> cs >> cf;
    cs--;
    cf--;

    dp[1][1] = 1;
    forn(i, 1, n) {
        forn(j, 1, n) {
            if (i == cs || i == cf) {
                cadd(dp[i + 1][j + 1], dp[i][j]);
                cadd(dp[i + 1][j], dp[i][j]);
            } else {
                if (j >= 2) {
                    cadd(dp[i + 1][j - 1], mul(dp[i][j], j - 1));
                }
                cadd(dp[i + 1][j + 1], mul(dp[i][j], j + 1 - (i > cs) - (i > cf)));
            }
        }
    }

    cout << dp[n][1];

    return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'Int main(Int, char**)':
kangaroo.cpp:19:29: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   19 | #define forn(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                             ^
kangaroo.cpp:61:5: note: in expansion of macro 'forn'
   61 |     forn(i, 1, n) {
      |     ^~~~
kangaroo.cpp:19:29: warning: unnecessary parentheses in declaration of 'j' [-Wparentheses]
   19 | #define forn(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                             ^
kangaroo.cpp:62:9: note: in expansion of macro 'forn'
   62 |         forn(j, 1, n) {
      |         ^~~~

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