# What should be the reason to get Wrong Answer in the UVa site for this program? [closed]

Here you'll find the problem: http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=614

#include<iostream>
#include<stack>
#include<string>
#include<cstdio>

/*farnaws,C++,673,08/12/2012*/

using namespace std;

string verifier(string input_line)
{

stack <char> braces;
int flag=0, count_left_first_brace=0,count_left_third_brace=0;
for(int i=0; i<input_line.size(); i++)
{

if(input_line[i]=='(' || input_line[i]=='[')
{
braces.push(input_line[i]);
if(input_line[i]=='(')
{
count_left_first_brace++;
}
else if(input_line[i]=='[')
{
count_left_third_brace++;
}

}
else if(input_line[i]==')' || input_line[i]==']')
{
if(!(braces.empty()==true))
{
if((input_line[i]==')' && braces.top()=='(') || (input_line[i]==']' && braces.top()=='[') )
{
braces.pop();
}

}

if(input_line[i]==')')
{
count_left_first_brace--;
}
else if(input_line[i]==']')
{
count_left_third_brace--;
}
}

}
if((braces.size()==0 && count_left_third_brace>=0 && count_left_first_brace>=0) || input_line.empty())
{
return "Yes";
}
else
{
return "No";
}

}
int main()
{

char line[128];
int limit;
cin>>limit;
getchar();
for(int i=0; i<limit; i++)
{
cin.getline(line,sizeof(line));
string str=line;
cout<<verifier(str)<<endl;
}

return 0;

}

-

## closed as off topic by ANeves, Brian Reichle, Jeff Vanzella, Glenn Rogers, Anton GolovDec 11 '12 at 22:28

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Here's a style review, with a glance at efficiency. Not going to check for correctness, as that's outside the scope of the site. I'll start from main.

char line[128];


Why not use an std::string here? You're creating one later anyway; using it directly and passing by const reference would not be any slower.

getchar();


Either use streams, or use C-style IO; don't mix the two. Besides, streams have a perfectly good function to do this.

cin.getline(line, sizeof(line));


Don't do this. Do this instead:

std::getline(std::cin, line); // here, line should be an std::string


I would also not have verifier return a string; instead:

std::cout << (verifier(str) ? "Yes" : "No") << '\n';


(You have no reason to flush here.)

Moving onto the verifier function itself. A range-based for loop would be much more convenient:

for (char c : input_line) {
// logic
}


The flag variable is unused, as far as I can tell.

The if(!(braces.empty()==true)) could much better be written as

if (!braces.empty())


Your count_left_third_brace and count_right_third_brace variables are not necessary; you can determine whether the code is right based purely on the contents of the stack.

The function boils down to:

bool verifier(std::string const& str) {
std::stack<char> braces;
for (char c : str) {
switch (c) {
case '(':
case '[':
braces.push(c);
break;
case ')':
if (braces.empty() || braces.top() != '(')
return false;
braces.pop();
break;
case '[':
if (braces.empty() || braces.top() != ']')
return false;
braces.pop();
break;
}
}
return true;
}


This is mostly equivalent to the existing code, and is probably closer to the intent.

-
"Not going to check for correctness, as that's outside the scope of the site." Asking for code correctness is on-topic, as long as the code initially works. –  seand Dec 11 '12 at 20:00
@seand: From your link, "Correctness in unanticipated cases". Seeing as the OP has already discovered that there is some error, that error is off topic. –  Anton Golov Dec 11 '12 at 21:59
I have discovered the error and also solved the problem, thank you guys for your effort. –  MiNdFrEaK Dec 11 '12 at 22:12