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Submission #333748

# Submission time Handle Problem Language Result Execution time Memory
333748 2020-12-07T15:51:42 Z phathnv Kangaroo (CEOI16_kangaroo) C++11
100 / 100
 18 ms 14188 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 - 1][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
30.0 / 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 Correct 1 ms 492 KB Output is correct
4 Correct 1 ms 492 KB Output is correct
5 Correct 1 ms 640 KB Output is correct
6 Correct 1 ms 492 KB Output is correct
7 Correct 1 ms 492 KB Output is correct
8 Correct 1 ms 492 KB Output is correct
9 Correct 1 ms 492 KB Output is correct
10 Correct 1 ms 492 KB Output is correct
11 Correct 1 ms 492 KB Output is correct

Subtask #3
15.0 / 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 Correct 1 ms 492 KB Output is correct
4 Correct 1 ms 492 KB Output is correct
5 Correct 1 ms 640 KB Output is correct
6 Correct 1 ms 492 KB Output is correct
7 Correct 1 ms 492 KB Output is correct
8 Correct 1 ms 492 KB Output is correct
9 Correct 1 ms 492 KB Output is correct
10 Correct 1 ms 492 KB Output is correct
11 Correct 1 ms 492 KB Output is correct
12 Correct 1 ms 1260 KB Output is correct
13 Correct 1 ms 1132 KB Output is correct
14 Correct 1 ms 1280 KB Output is correct
15 Correct 1 ms 1260 KB Output is correct
16 Correct 1 ms 1260 KB Output is correct
17 Correct 1 ms 1260 KB Output is correct
18 Correct 1 ms 1132 KB Output is correct
19 Correct 1 ms 1260 KB Output is correct
20 Correct 2 ms 1260 KB Output is correct

Subtask #4
49.0 / 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 Correct 1 ms 492 KB Output is correct
4 Correct 1 ms 492 KB Output is correct
5 Correct 1 ms 640 KB Output is correct
6 Correct 1 ms 492 KB Output is correct
7 Correct 1 ms 492 KB Output is correct
8 Correct 1 ms 492 KB Output is correct
9 Correct 1 ms 492 KB Output is correct
10 Correct 1 ms 492 KB Output is correct
11 Correct 1 ms 492 KB Output is correct
12 Correct 1 ms 1260 KB Output is correct
13 Correct 1 ms 1132 KB Output is correct
14 Correct 1 ms 1280 KB Output is correct
15 Correct 1 ms 1260 KB Output is correct
16 Correct 1 ms 1260 KB Output is correct
17 Correct 1 ms 1260 KB Output is correct
18 Correct 1 ms 1132 KB Output is correct
19 Correct 1 ms 1260 KB Output is correct
20 Correct 2 ms 1260 KB Output is correct
21 Correct 4 ms 3840 KB Output is correct
22 Correct 4 ms 4076 KB Output is correct
23 Correct 4 ms 4460 KB Output is correct
24 Correct 18 ms 14188 KB Output is correct
25 Correct 17 ms 14188 KB Output is correct
26 Correct 17 ms 14188 KB Output is correct
27 Correct 17 ms 14080 KB Output is correct
28 Correct 13 ms 10220 KB Output is correct