Submission #125444

#	Time	Username	Problem	Language	Result	Execution time	Memory
125444		win11905	Kangaroo (CEOI16_kangaroo)	C++11	100 / 100	93 ms	31992 KiB

kangaroo

#include <bits/stdc++.h>
#define long long long
using namespace std;

const int M = 1e9+7;

const int N = 2e3+5;

int n, s, t;
long dp[N][N];

long solve(int i, int j) {
    if(j == 0) return 0;
    long &now = dp[i][j];
    if(now != -1) return now;
    if(i == 1) return now = (j == 1 ? 1 : 0);
    if(i == s || i == t) 
        return now = (solve(i-1, j-1) + solve(i-1, j)) % M;
    return now = (solve(i-1, j+1) * j + solve(i-1, j-1) * (j - (i > s ? 1 : 0) - (i > t ? 1 : 0))) % M; 
}

int main() {
    memset(dp, -1, sizeof dp);
    scanf("%d %d %d", &n, &s, &t);
    printf("%lld\n", solve(n, 1));
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:24:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d %d", &n, &s, &t);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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