OJ Board

Where is the operator defined? The class hierarchy is as follows: Which class is it defined in? I'm afraid I can't find it.

I read some manual and find that the operator >> returns *this, the type should be istream&. Then why can we put it in the while statement as a condition?

Oh, I've found the error. How careless I am.
I'm sorry.

#include <iostream>

using namespace std;

template <class ValueType> class ZKTreeNode{
private:
ValueType m_value;
ZKTreeNode<ValueType>* m_parent;
ZKTreeNode<ValueType>* m_lch;
ZKTreeNode<ValueType>* m_rch;

public:
ZKTreeNode(){
m_parent = NULL;
m_lch = NULL;
m_rch = NULL ...

Thank you very much!

#include <iostream.h>
void main(){
int a;
while(true){
cin>>a;
if(cin.fail()){
cout<<"error"<<endl;
cin.clear();
}
else{
break;
}
}
}

When the input is
a

Why the output is
error
error
error
error
error
error
error
error
error
error
error
...
I do use the cin.clear()! But why still ...

Oh, I see. I can use cin.fail() to see whether there is an input error, and use cin.clear to make the cin>> work again.
Thank you.

My C program runs well. But when I modify it to C++ version, it doesn't work. The reason is that I don't understand the "iostream" very well.
This is my program which is used to input a Tree from keyboard. For example:
if the tree is:
1
/
2
/ \
3 4

Then I can input :
(1 (2 (3 () () ) (4 ...

I think the job of this problem is: to find if there is a circle(a path from one node to itself) of odd edges.

Please read my algorithm , and help me to find the bug, or if it losts precision.
/*all the datas are of long double type*/
infinity=9999999999;
if(x_tree==0)
k_tree=infinity;
else
k_tree=y_tree/x_tree;
if(k_tree==infinity)
{
k_R=sqrt(y_tree*y_tree-r_tree*r_tree)/r_tree;
k_L=k_R*-1.0;
/*k_L ...

I use Floyd-Worshall to search if there is any circle (a path from a node to itself) with odd nodes. If there is, return no. And I get AC.

Another question:
If the result is 0.00000001, should I print 0.000 of 0.001? I mean though the distance is very little, but at least it exists. And 0.000 means the house can not be protected. That is not suitable to the distance less than 0.0005.

Input: My output: Is that right?
Can anyone give me some more test IO?

Thanks, I've found the bug of my program and got AC. The length of the name doesn't cause the bug as you expect. Thank you again.

I know the city name is very long. So I just read the first letter of each name and skip the other letters. But still the Runtime Error (SIGSEGV)

int case,m,n;
char city1,city2,c;
scanf("%d",&case);
while(case-->0){
scanf("%d %d",&m,&n);
c=getchar();/*eat the '\n'*/
while(m-->0){
city1 ...