HDU 1427（速算24点）

#include <iostream>
#include <algorithm>
using namespace std;

char s[5]; //输入字符
int num[4]; //字符对应的数字
int flag; //是否有解

//将输入字符转换为对应数字
void convert(int i)
{
	if (s[0] == 'A')
		num[i] = 1;
	else if (s[0] == 'J')
		num[i] = 11;
	else if (s[0] == 'Q')
		num[i] = 12;
	else if (s[0] == 'K')
		num[i] = 13;
	else if (s[0] == '1' && s[1] == '0')
		num[i] = 10;
	else
		num[i] = s[0] - '0';
}

//深搜
void DFS(int sum, int id, int tmp)
{
	if (flag)
		return;
	if (id == 3)
	{
		if (sum + tmp == 24 || sum - tmp == 24 || sum * tmp == 24)
			flag = 1;
		if (tmp != 0 && sum % tmp == 0 && sum / tmp == 24)
			flag = 1;
		return;
	}

	//先计算前半部分
	DFS(sum + tmp, id + 1, num[id + 1]);
	DFS(sum - tmp, id + 1, num[id + 1]);
	DFS(sum * tmp, id + 1, num[id + 1]);
	if (tmp != 0 && sum % tmp == 0)
		DFS(sum / tmp, id + 1, num[id + 1]);
	//先计算后半部分
	DFS(sum, id + 1, tmp + num[id + 1]);
	DFS(sum, id + 1, tmp - num[id + 1]);
	DFS(sum, id + 1, tmp * num[id + 1]);
	if (num[id + 1] != 0 && tmp % num[id + 1] == 0)
		DFS(sum, id + 1, tmp / num[id + 1]);
}

int main()
{
	while (cin >> s)
	{
		convert(0);
		for (int i = 1; i < 4; i++)
		{
			cin >> s;
			convert(i);
		}

		sort(num, num + 4);
		flag = 0;

		DFS(num[0], 1, num[1]);
		while (next_permutation(num, num + 4) && flag == 0)
			DFS(num[0], 1, num[1]);

		if (flag)
			cout << "Yes" << endl;
		else
			cout << "No" << endl;
	}
	return 0;
}