Ultraviolet A 839 Not so Mobile (recursive input of the tree), uva839

Ultraviolet A 839 Not so Mobile (recursive input of the tree), uva839

Determine if a tree balance is balanced. In each test example, there are 4 wl, dl, wr in each row, dr when wl * dl = wr * dr, this balance is considered as this balance. When wl or wr is equal to 0, the next line will be a sub-balance. If the sub-balance wl is the sub-balance's wl + wr, otherwise the entire balance is unbalanced.

It is easy to see that the input is recursive, so we can directly recursive the input edge to judge.

#include<cstdio>using namespace std;bool solve(int &w){    int wl, dl, wr, dr;    bool mobl = true, mobr = true;    scanf("%d %d %d %d", &wl, &dl, &wr, &dr);    if(!wl) mobl = solve(wl);    if(!wr) mobr = solve(wr);    w = wl + wr;    return mobl && mobr && (wl * dl == wr * dr);}int main(){    int cas, w;    scanf("%d", &cas);    while(cas--)    {        printf(solve(w) ? "YES\n" : "NO\n");        if(cas) printf("\n");    }    return 0;}

Not so Mobile

Before being an ubiquous communications gadget,MobileWas 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 has strates a simple mobile. it is just a wire, suincluded 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 isWL×DL =WR×DRwhereDL is the left distance,DR is the right distance,WL is the left weight andWR 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:WLDLWRDR

IfWL orWR is zero then there is a sub-mobile hanging from that end and the following lines define 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 bothWL andWRare 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

10 2 0 40 3 0 11 1 1 12 4 4 21 6 3 2

Sample Output

YES

Not so Mobile

Before being an ubiquous communications gadget,MobileWas 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 has strates a simple mobile. it is just a wire, suincluded 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 isWL×DL =WR×DRwhereDL is the left distance,DR is the right distance,WL is the left weight andWR 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:WLDLWRDR

IfWL orWR is zero then there is a sub-mobile hanging from that end and the following lines define 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 bothWL andWRare 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

10 2 0 40 3 0 11 1 1 12 4 4 21 6 3 2

Sample Output

YES