提出 #21899896

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ソースコード 拡げる

#include <bits/stdc++.h>
#define i64 long long
#define sz(a) int((a).size())
#define all(a) (a).begin(), (a).end()
#define rep(i, a, b) for (int i = (a); i < (b); ++i)
#define per(i, a, b) for (int i = (b) - 1; i >= (a); --i)
using namespace std;

const int N = 62;
int n, nz;
i64 f[N][N * N / 4][N], c[N][N];
// f[i][j][k] : i points, j zero-secs, k strings 
// i < n * 2 + 2, j < n * n + 1, k < n + 2

int main() {
	// freopen("ARC117E.in", "r", stdin); //
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	cin >> n >> nz; // n +1's and n -1's, 2 * n + 1 points
	rep(i, 0, n + 1) {
		c[i][0] = c[i][i] = 1;
		rep(j, 1, i) {c[i][j] = c[i - 1][j] + c[i - 1][j - 1];}
	}
	f[0][0][0] = 1;
	rep(i, 0, n * 2 + 2) {
		rep(j, 0, n * n + 1) {
			rep(k, 0, n + 2) {
				if (!f[i][j][k]) {continue;}
				rep(d, k + 1, min(n + 1, 2 * n + 1 - i) + 1) {
					f[i + d][j + d * (d - 1) / 2][d - k]
					 += f[i][j][k] * c[d - 1][k];
				}
			}
		}
	}
	i64 res = 0;
	rep(i, 0, n * 2 + 2) {
		rep(j, 0, n * n + 1) {
			rep(k, 0, n + 2) {
				if (!f[i][j][k]) {continue;}
				if (!k or j > nz) {continue;}
				res += f[i][j][k] * f[n * 2 + 1 - i][nz - j][k - 1];
			}
		}
	}
	cout << res << '\n';
	return 0;
}

/* 📌https://www.cnblogs.com/George1123/p/tips.html */

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