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Submission #333747

# Submission time Handle Problem Language Result Execution time Memory
333747 2020-12-07T15:49:51 Z phathnv Kangaroo (CEOI16_kangaroo) C++11
6 / 100
 1 ms 492 KB 
#include <bits/stdc++.h>

#define mp make_pair
#define X first
#define Y second
#define taskname "kangaroo"

using namespace std;

typedef long long ll;
typedef pair <int, int> ii;

const int N = 2001;
const int MOD = 1e9 + 7;

int sum(int a, int b){
    a += b;
    a -= (a >= MOD) * MOD;
    return a;
}

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

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

void readInput(){
    cin >> n >> cs >> cf;
}

void solve(){
    dp[0][0] = 1;
    int fixed = 0;
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= i; j++)
            if (i == cs || i == cf)
                dp[i][j] = (dp[i - 1][j] + dp[i][j - 1]) % MOD;
            else
                dp[i][j] = sum(mul(dp[i - 1][j + 1], j), mul(dp[i - 1][j - 1], j - fixed));
        fixed += (i == cs || i == cf);
    }
    cout << dp[n][1];
}

int main(){
    if (fopen(taskname".inp", "r")){
        freopen(taskname".inp", "r", stdin);
        freopen(taskname".out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    readInput();
    solve();
    return 0;
}

Compilation message

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:48:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   48 |         freopen(taskname".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:49:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   49 |         freopen(taskname".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 364 KB Output is correct
2 Correct 1 ms 364 KB Output is correct

Subtask #2
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 364 KB Output is correct
2 Correct 1 ms 364 KB Output is correct
3 Incorrect 1 ms 492 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #3
0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 364 KB Output is correct
2 Correct 1 ms 364 KB Output is correct
3 Incorrect 1 ms 492 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #4
0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 364 KB Output is correct
2 Correct 1 ms 364 KB Output is correct
3 Incorrect 1 ms 492 KB Output isn't correct
4 Halted 0 ms 0 KB -