Submission #860904

#	Time	Username	Problem	Language	Result	Execution time	Memory
860904		blackslex	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	40 ms	55132 KiB

kangaroo

#include<bits/stdc++.h>

using namespace std;
using ll = long long;

const int N = 2005, M = 1e9 + 7;
ll n, cs, cf, dp[N][N][3];

int main() {
    scanf("%lld %lld %lld", &n, &cs, &cf);
    if (cs == 1 || cf == 1) dp[1][1][1] = 1;
    else dp[1][1][0] = 1;
    for (int i = 1; i <= n; i++) {
        if (i + 1 == cs || i + 1 == cf) {
            for (int j = 1; j <= i; j++) {
                for (int k = 0; k < 2; k++) {
                    dp[i + 1][j + 1][k + 1] += dp[i][j][k]; dp[i + 1][j + 1][k + 1] %= M; // fix, no merge
                    dp[i + 1][j][k + 1] += dp[i][j][k]; dp[i + 1][j][k + 1] %= M; // fix, merge
                }
            }
        } else {
            for (int j = 1; j <= i; j++) {
                for (int k = 0; k < 3; k++) {
                    dp[i + 1][j + 1][k] += (j + 1 - k) * dp[i][j][k]; dp[i + 1][j + 1][k] %= M; // insert, no merge
                    dp[i + 1][j - 1][k] += (j - 1) * dp[i][j][k]; dp[i + 1][j - 1][k] %= M; // insert, merge
                }
            }
        }
    }
    printf("%lld", dp[n][1][2]);
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:10:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   10 |     scanf("%lld %lld %lld", &n, &cs, &cf);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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