34
votes
Accepted
Balanced parentheses
This is almost all style suggestions; the code itself looks great.
Personally, I prefer the brace-on-same-line style for everything in JS, and I prefer proper blocks instead of inlining expressions. ...
- 32.9k
33
votes
Stack data structure in Python 3
From a pure Python standpoint, a list is already a stack if you narrow its methods down to only pop and append.
...
- 441
31
votes
A counterexample in balanced parentheses
May I suggest a simpler solution:
You need only a counter. it is incremented by 1 whenever you encounter an openning parenthesis "(" and is decreased by 1 whenever you encounter a closing parenthesis ...
- 3,217
28
votes
Accepted
Stack implementation using Swift
Let's start with some general remarks:
Swift does not require semicolons after statements (but they are allowed). From what I have seen since Swift was introduced last year,
most people do not write ...
- 22.2k
25
votes
Accepted
HackerRank Implement Queue using two stacks Solution
Algorithmic complexity for combined operations
Containers are interesting elements in most programming languages: they have an internal state, namely their elements and therefore their size.
This ...
- 18.8k
23
votes
Accepted
Implementing a Stack with Templates and Smart pointers
Readability
Please put a space after the include and before the <
...
- 91.5k
21
votes
Accepted
Reversing a String using Stack
Unicode is hard to get right, especially in Java as it has a more or less broken concept of a “character”. An Unicode code point is a 21-bit number. These code points are encoded to bytes with the UTF-...
- 12.4k
20
votes
Accepted
Simple Stack implementation in C++
Your stack implementation is terrible, and so is @hc_dev: neither handles memory correctly.
Resource Handling
It is generally frowned upon to call new and ...
- 3,493
19
votes
Balanced parentheses using standard C++
Avoid using namespace std; - it's a large namespace, and growing as new C++ standards appear. Bringing all its names into the global namespace completely obviates ...
- 57.6k
18
votes
Accepted
Implementing a Stack in Java for a technical interview
A stack should not know about the first element. A stack only know about the last element that was pushed, so the Stack object itself should only have one ...
- 339
18
votes
Accepted
Stack implementation using a linked list
Time complexity
The time complexity of push and pop operations should be \$O(1)\$, and so it is in your case too. It doesn't matter how many elements you have, these operations should take constant ...
- 107k
18
votes
Stack class in Java 8
Other answers correctly point out that using primitive types and not mixing them with Objects (=int instead of Integer), ...
- 281
17
votes
Reversing a String using Stack
This question provides a really good example of how learning 'tools' is important, but understanding efficiency is better.
The purpose of the task was probably to teach you to use a stack, but there ...
- 96.7k
16
votes
Accepted
Check for balanced parentheses
I just wanted to write that the code looks completely fine to me, until...
assertEquals(false, isBalanced("[["));
I''m sure you'll find the error :-)
...
- 10.3k
16
votes
Leetcode: Valid parentheses
This is a follow up of @Henrik Hansen. Instead, of a switch I would use a Dictionary<T, K>. A Dictionary offers two main advantages: an increase readibility ...
- 541
15
votes
Implementation of stack using pointers
Please fix your indentation all over the header. It should be consistent with everything else.
You don't need the return 0 at the end of ...
- 34.7k
14
votes
Accepted
Stack implementation using an array
sscanf is not safe
It's not part of your stack but part of your driver code, but scanf() is not a good function to use. There are many reasons for this, but the ...
- 64.1k
14
votes
Accepted
Implementation of stack using pointers
First of all, I will start with one of the most common remarks: please, do not use using namespace std;. It is especially bad if you write it in a header file since ...
- 19.8k
14
votes
Implementing a Stack in Java for a technical interview
As usual, revewing a design rather than code.
As coded, pop takes time proportional to the current stack size. It could and should take constant time. Hint: ...
- 52.9k
14
votes
Accepted
Very simple stack in C
I see a number of things that may help you improve your code.
Use a stack pointer as a parameter
Right now, one can only have one stack at a time. Worse, if one calls ...
- 64.1k
14
votes
Accepted
Checking for parentheses balance in C
Bugs
The loop header is wrong:
for(i=0;line[i]!=NULL;i++){
Here, you want to scan until you find a byte with ASCII value 0 (also called an ASCII NUL, and ...
- 142k
14
votes
Array-based stack
The methods named emptyCheck() and fullCheck() are ambiguous. They should be named isEmpty() ...
- 453
14
votes
Stack data structure in Python 3
On the whole the code is good, but I would look for three improvements:
Information-hiding: I would change self.stack to ...
- 249
13
votes
13
votes
Reversing a String using Stack
@amon wrote a great answer. With Java 8, handling of surrogate pairs is even easier. There is a codePoints() method on the CharSequence interface.
...
- 541
13
votes
Accepted
Java and C++ stack implementations with dramatically different performance
Performance
I'll get to a bit of a review, but first, since you're most interested in performance, I've done some benchmarking. In short, all evidence points towards maaartinus' theory being the ...
- 10.5k
13
votes
Accepted
StackList<T> implementation
Issues
public void Push(T item)
{
_stackList.Insert(0, item);
}
The hurts the stack list.
It would be much easier if you just added new items at the end of ...
- 43.8k
13
votes
Checking for parentheses balance in C
The idea is correct, the implementation is not.
Upon exiting the loop you need to test for pilepointer == -1. Otherwise, the strings like ...
- 52.9k
13
votes
Stack data structure in Python 3
The code is clean. My major concern with how it looks is that your naming doesn't follow PEP8. Names should be snake_case, not camelCase. So isEmpty should be ...
- 16.1k
Only top scored, non community-wiki answers of a minimum length are eligible