제출 #938756

#제출 시각아이디문제언어결과실행 시간메모리
938756Doncho_Bonboncho캥거루 (CEOI16_kangaroo)C++17
100 / 100
13 ms32348 KiB
#include <bits/stdc++.h> using namespace std; template< class T, class T2 > inline bool chkmin( T& a, const T2& b ){ return a > b ? a = b, 1 : 0; } template< class T, class T2 > inline bool chkmax( T& a, const T2& b ){ return a < b ? a = b, 1 : 0; } #ifndef LOCAL #define cerr if( false )cerr #endif #define out(x) #x << " = " << x << " " typedef long long ll; const int MAX_N = 2048; const ll mod = 1e9 + 7; ll dp[MAX_N][MAX_N]; int main (){ #ifndef LOCAL std::ios_base::sync_with_stdio( false ); std::cin.tie( NULL ); std::cout.tie( NULL ); #endif int n, S, E; std::cin >> n >> S >> E; dp[1][1] = 1; for( int i=2 ; i <= n ; i++ ){ for( int j=1 ; j <= i ; j ++ ){ if( i == S || i == E ){ dp[i][j] = ( dp[i-1][j-1] + dp[i-1][j] ) % mod; }else{ dp[i][j] = ( dp[i-1][j+1] * j ) % mod; dp[i][j] += ( dp[i-1][j-1] * ( j - ( S < i ) - ( E < i ) ) ) %mod; if( dp[i][j] >= mod ) dp[i][j] -= mod; } } } std::cout << dp[n][1] << endl; return 0; }
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