CODEWITHSUNDEEP
c++stack
John Smith
John Smith

Reputation: 63

Cannot Retrieve Everything out of a Stack

I'm having a little trouble understanding why this code does not output as I expected? Any ideas?

Output: ? you are

Expected: ? you are how Hello, 

#include <iostream> 
#include <stack> 
#include <string> 
using namespace std; 

 int main() 
 { 
     stack<string> sentence; 

     sentence.push("Hello,"); 
     sentence.push("how"); 
     sentence.push("are"); 
     sentence.push("you"); 
     sentence.push("?"); 

     for (int i=0; i<sentence.size(); ++i) { 
         cout << sentence.top() << " "; 
         sentence.pop(); 
     } 
     cout << endl; 

     return 0; 
 }

Upvotes: 1

Views: 56

Answers (3)

SigTerm
SigTerm

Reputation: 26419

Because calling sentence.pop() decreases stack size by 1 AND you're increasing i at the same time. You'll only get half of the values this way.

Do this instead:

 while (!sentence.empty()){ 
     cout << sentence.top() << " "; 
     sentence.pop(); 
 }

Upvotes: 4

Vlad from Moscow
Vlad from Moscow

Reputation: 310980

When you issue pop() the size of the stack is decremented while variable i is increased independently of the size of the stack. I advice to substitute your loop for the following one

 while  ( !sentence.empty() ) { 
     cout << sentence.top() << " "; 
     sentence.pop(); 
 }

Upvotes: 2

Ben S.
Ben S.

Reputation: 1143

When you're popping the stack inside the loop, you're changing it's size, affecting how many times the loop executes.

I would instead do:

while (!sentence.empty())
{
    cout << sentence.top() << " ";
    sentence.pop();
}

Upvotes: 0

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