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Submission #236752

# Submission time Handle Problem Language Result Execution time Memory
236752 2020-06-03T08:14:02 Z Sorting Kangaroo (CEOI16_kangaroo) C++14
100 / 100
 50 ms 31736 KB 
#include <bits/stdc++.h>

using namespace std;

const int k_N = 2000 + 3;
const int k_Mod = 1e9 + 7;

int n, cs, cf;
long long dp[k_N][k_N];

void fix(long long &x){
    x = (x >= k_Mod) ? (x - k_Mod) : x;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> n >> cs >> cf;
    //cs--, cf--;
    if(cs > cf)
        swap(cs, cf);

    for(int pos = 0; pos <= n; ++pos){
        for(long long group = 0; group <= n; ++group){
            long long &answer = dp[pos][group];
            if(pos == 0){
                answer = (group == 1);
                continue;
            }

            answer = 0;

            if(pos > cf){
                answer = dp[pos - 1][group + 1];
                if(group >= 2){
                    answer += dp[pos - 1][group - 1] * group % k_Mod * (group - 1) % k_Mod;
                    fix(answer);
                }
            }
            else if(pos == cf){
                answer = dp[pos - 1][group + 1];
                answer += dp[pos - 1][group] * group % k_Mod;
                fix(answer);
            }
            else if(pos > cs){
                answer = dp[pos - 1][group + 1];
                if(group >= 2){
                    answer += dp[pos - 1][group - 1] * (group - 1) % k_Mod * (group - 1) % k_Mod;
                    fix(answer);
                }
            }
            else if(pos == cs){
                answer = dp[pos - 1][group + 1];
                if(pos != 1){
                    if(group)
                        answer += dp[pos - 1][group] * (group - 1) % k_Mod;
                }
                else
                    answer += dp[pos - 1][group] * group % k_Mod;
                fix(answer);
            }
            else if(pos < cs){
                answer = dp[pos - 1][group + 1];
                if(group >= 2){
                    if(pos == 1)
                        answer += dp[pos - 1][group - 1] * (((group * group % k_Mod - 3 * group + 3) % k_Mod + k_Mod) % k_Mod) % k_Mod;
                    else
                        answer += dp[pos - 1][group - 1] * (((group * group % k_Mod - 3 * group + 2) % k_Mod + k_Mod) % k_Mod) % k_Mod;
                    fix(answer);
                }
            }

            //cout << answer << " - " << pos << " " << group << endl;
        }
    }

    cout << dp[n][0] << "\n";
}

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 384 KB Output is correct
2 Correct 5 ms 384 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 384 KB Output is correct
2 Correct 5 ms 384 KB Output is correct
3 Correct 5 ms 384 KB Output is correct
4 Correct 4 ms 512 KB Output is correct
5 Correct 5 ms 512 KB Output is correct
6 Correct 5 ms 512 KB Output is correct
7 Correct 5 ms 512 KB Output is correct
8 Correct 4 ms 512 KB Output is correct
9 Correct 4 ms 512 KB Output is correct
10 Correct 4 ms 512 KB Output is correct
11 Correct 5 ms 512 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 384 KB Output is correct
2 Correct 5 ms 384 KB Output is correct
3 Correct 5 ms 384 KB Output is correct
4 Correct 4 ms 512 KB Output is correct
5 Correct 5 ms 512 KB Output is correct
6 Correct 5 ms 512 KB Output is correct
7 Correct 5 ms 512 KB Output is correct
8 Correct 4 ms 512 KB Output is correct
9 Correct 4 ms 512 KB Output is correct
10 Correct 4 ms 512 KB Output is correct
11 Correct 5 ms 512 KB Output is correct
12 Correct 5 ms 1536 KB Output is correct
13 Correct 5 ms 1408 KB Output is correct
14 Correct 5 ms 1408 KB Output is correct
15 Correct 5 ms 1536 KB Output is correct
16 Correct 5 ms 1536 KB Output is correct
17 Correct 5 ms 1408 KB Output is correct
18 Correct 5 ms 1280 KB Output is correct
19 Correct 5 ms 1408 KB Output is correct
20 Correct 6 ms 1408 KB Output is correct

Subtask #4
49.0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 384 KB Output is correct
2 Correct 5 ms 384 KB Output is correct
3 Correct 5 ms 384 KB Output is correct
4 Correct 4 ms 512 KB Output is correct
5 Correct 5 ms 512 KB Output is correct
6 Correct 5 ms 512 KB Output is correct
7 Correct 5 ms 512 KB Output is correct
8 Correct 4 ms 512 KB Output is correct
9 Correct 4 ms 512 KB Output is correct
10 Correct 4 ms 512 KB Output is correct
11 Correct 5 ms 512 KB Output is correct
12 Correct 5 ms 1536 KB Output is correct
13 Correct 5 ms 1408 KB Output is correct
14 Correct 5 ms 1408 KB Output is correct
15 Correct 5 ms 1536 KB Output is correct
16 Correct 5 ms 1536 KB Output is correct
17 Correct 5 ms 1408 KB Output is correct
18 Correct 5 ms 1280 KB Output is correct
19 Correct 5 ms 1408 KB Output is correct
20 Correct 6 ms 1408 KB Output is correct
21 Correct 10 ms 6400 KB Output is correct
22 Correct 12 ms 7040 KB Output is correct
23 Correct 12 ms 7808 KB Output is correct
24 Correct 47 ms 31736 KB Output is correct
25 Correct 50 ms 31736 KB Output is correct
26 Correct 46 ms 31736 KB Output is correct
27 Correct 41 ms 31608 KB Output is correct
28 Correct 31 ms 23928 KB Output is correct