Submission #1842850

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Source Code Expand

#include <cstdio>
#include <iostream>
#include <algorithm>

inline int Get() {
	char ch;
	while ((ch = getchar()) < '0' || ch > '9');
	int Num = ch - '0';
	while ((ch = getchar()) >= '0' && ch <= '9')
		Num = (Num << 3) + (Num << 1) + ch - '0';
	return Num;
}
const int N = 55;
const int Mod = 1e9 + 7;
int n, a[N], g[N][N << 1][N << 1], ans;
int main() {
	n = Get();
	for (int i = 1; i < n * 2; ++i) a[i] = Get();
	std :: sort(a + 1, a + n * 2);
	
	g[0][1][0] = 1;
	for (int i = 1, w; i < n; ++i) 
		for (int j = 1; j < i * 2; ++j)
			for (int k = 0; k < j; ++k)
				if (w = g[i - 1][j][k]) {
					int x = j, y = k;
					if (a[n - i] != a[n - i + 1]) ++x, ++y;
					if (a[n + i] != a[n + i - 1]) ++x;
					for (int p = 0; p < x; ++p)
						(g[i][x - std :: max(abs(y - p) - 1, 0)][p <= y ? p : y + 1] += w) %= Mod;
				}
				
	for (int i = 1; i < n * 2; ++i)
		for (int k = 0; k < i; ++k) (ans += g[n - 1][i][k]) %= Mod;
	
	printf("%d\n", ans);
}

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Judge Result