Not so Mobile （针对递归输入的函数）

 

 

Before being an ubiquous communications gadget, a mobile was just a structure made of strings and wires suspending colourfull things. This kind of mobile is usually found hanging over cradles of small babies.

 

The figure illustrates a simple mobile. It is just a wire, suspended by a string, with an object on each side. It can also be seen as a kind of lever with the fulcrum on the point where the string ties the wire. From the lever principle we know that to balance a simple mobile the product of the weight of the objects by their distance to the fulcrum must be equal. That is W_l×D_l = W_r×D_r where D_l is the left distance, D_r is the right distance, W_l is the left weight and W_r is the right weight.

 

In a more complex mobile the object may be replaced by a sub-mobile, as shown in the next figure. In this case it is not so straightforward to check if the mobile is balanced so we need you to write a program that, given a description of a mobile as input, checks whether the mobile is in equilibrium or not.

 

 

Input 

The input begins with a single positive integer on a line by itself indicating the number of the cases following, each of them as described below. This line is followed by a blank line, and there is also a blank line between two consecutive inputs.

 

 

 

The input is composed of several lines, each containing 4 integers separated by a single space. The 4 integers represent the distances of each object to the fulcrum and their weights, in the format: W_l D_l W_r D_r

If W_l or W_r is zero then there is a sub-mobile hanging from that end and the following lines define the the sub-mobile. In this case we compute the weight of the sub-mobile as the sum of weights of all its objects, disregarding the weight of the wires and strings. If both W_l and W_r are zero then the following lines define two sub-mobiles: first the left then the right one.

 

Output 

For each test case, the output must follow the description below. The outputs of two consecutive cases will be separated by a blank line.

 

 

 

Write `YES' if the mobile is in equilibrium, write `NO' otherwise.

 

Sample Input 

1

0 2 0 4
0 3 0 1
1 1 1 1
2 4 4 2
1 6 3 2

 

Sample Output 

YES

 

 针对递归输入的函数

#include <iostream>
using namespace std;

bool solve(int &W)
{
    int W1,W2,D1,D2;
    cin>>W1>>D1>>W2>>D2;
    bool b1=true,b2=true;
    if(W1==0) b1=solve(W1);
    if(W2==0) b2=solve(W2);
    W=W1+W2;
    return b1&&b2&&(W1*D1==W2*D2);
}

int main()
{
    int T,W;
    cin>>T;
    while(T--)
    {
     if(solve(W)) cout<<"YES\n";
     else         cout<<"NO\n";
     if(T)        cout<<"\n";
    }
    return 0;
}