HDU 1579（Function Run Fun）

动态规划题。

#include <iostream>
#include <cstring>
using namespace std;
const int MAXN = 25;

int dp[MAXN][MAXN][MAXN];

void init()
{
	for (int a = 0; a <= 20; a++)
	{
		for (int b = 0; b <= 20; b++)
		{
			for (int c = 0; c <= 20; c++)
			{
				if (a == 0 || b == 0 || c == 0)
					dp[a][b][c] = 1;
				else if (a < b && b < c)
					dp[a][b][c] = dp[a][b][c - 1] + dp[a][b - 1][c - 1] - dp[a][b - 1][c];
				else
					dp[a][b][c] = dp[a - 1][b][c] + dp[a - 1][b - 1][c] + dp[a - 1][b][c - 1] - dp[a - 1][b - 1][c - 1];
			}
		}
	}
}

int main()
{
	memset(dp, 0, sizeof(dp));
	init();
	int a, b, c;
	while (cin >> a >> b >> c)
	{
		if (a == -1 && b == -1 && c == -1)
			break;
		else if (a <= 0 || b <= 0 || c <= 0)
			cout << "w(" << a << ", " << b << ", " << c << ") = " << 1 << endl;
		else if (a > 20 || b > 20 || c > 20)
			cout << "w(" << a << ", " << b << ", " << c << ") = " << dp[20][20][20] << endl;
		else
			cout << "w(" << a << ", " << b << ", " << c << ") = " << dp[a][b][c] << endl;
	}
	return 0;
}

继续加油。