QBCOND - Quan hệ có điều kiện

Tác giả: happyboy99x

Ngôn ngữ: C++

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vii> vvii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long long LL;

#define sz(a) (int((a).size()))
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define all(c) (c).begin(), (c).end()
#define tr(c,i) for(typeof((c).begin()) i = (c).begin(), _e = (c).end(); i != _e; ++i)
#define present(c,x) ((c).find(x) != (c).end())
#define cpresent(c,x) (find(all(c),x) != (c).end())
#define rep(i,n) for(int i = 0, _n = (n); i < _n; ++i)
#define repd(i,n) for(int i = (n)-1; i >= 0; --i )
#define fo(i,a,b) for(int i = (a), _b = (b); i <= _b; ++i)
#define fod(i,a,b) for(int i = (a), _b = (b); i >= _b; --i)

#define INF 1000000000
#define N 15

bool hc[N][N*(N-1)/2];
int f[N][N*(N-1)/2];

int F(int n, int k) {
	int & res = f[n][k];
	if(hc[n][k]) return res;
	hc[n][k] = 1;
	LL c = 1;
	for(int i = 1; i <= n && i*(i-1)/2 <= k; ++i) {
		c = c * (n-i+1) / i;
		res += c * F(n-i, k - i*(i-1)/2);
	}
	return res;
}

int main() {
	//freopen( "input.txt", "r", stdin );
	//freopen( "output.txt", "w", stdout );
	hc[0][0] = f[0][0] = 1;
	fo(i,1,10) { hc[i][0] = 1; f[i][0] = i * f[i-1][0]; }
	int n; LL k;
	while(scanf("%d%lld",&n,&k)==2 && n != -1) {
		printf("%d\n", n*(n-1)/2 < k ? 0 : F(n, k));
	}
	return 0;
}

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