Grokking Data Structures & Algorithms for Coding Interviews

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Solution: Sorting a Stack

Problem Statement

Given a stack, sort it using only stack operations (push and pop).

You can use an additional temporary stack, but you may not copy the elements into any other data structure (such as an array). The values in the stack are to be sorted in descending order, with the largest elements on top.

Examples

1. Input: [34, 3, 31, 98, 92, 23]
   Output: [3, 23, 31, 34, 92, 98]

2. Input: [4, 3, 2, 10, 12, 1, 5, 6]
   Output: [1, 2, 3, 4, 5, 6, 10, 12]

3. Input: [20, 10, -5, -1]
   Output: [-5, -1, 10, 20]

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Leszek Kalwa

Leszek Kalwa

· 2 years ago

Guys,

Either you treat stack as a stack, or as an array. What the heck is line:15 from your js solution? That's clearly accessing something by index.

            // While the temporary stack is not empty and the top element
            // of the temporary stack is greater than the current element,
            // push elements from the temporary stack back to the original stack.
            while (tempStack.length && tempStack[tempStack.length - 1] > temp) {
                stack.push(tempStack.pop());
            }
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