Sort a stack using a temporary stack
Given a stack of integers, sort it in descending order using another temporary stack.
Examples:
Input : [34, 3, 31, 98, 92, 23] Output : [3, 23, 31, 34, 92, 98] Input : [3, 5, 1, 4, 2, 8] Output : [1, 2, 3, 4, 5, 8]
We follow this algorithm.
- Create a temporary stack say tmpStack.
- While input stack is NOT empty do this:
- Pop an element from input stack call it temp
- while temporary stack is NOT empty and top of temporary stack is greater than temp,
pop from temporary stack and push it to the input stack - push temp in temporary stack
- The sorted numbers are in tmpStack
Here is a dry run of above pseudo code.
input: [34, 3, 31, 98, 92, 23] Element taken out: 23 input: [34, 3, 31, 98, 92] tmpStack: [23] Element taken out: 92 input: [34, 3, 31, 98] tmpStack: [23, 92] Element taken out: 98 input: [34, 3, 31] tmpStack: [23, 92, 98] Element taken out: 31 input: [34, 3, 98, 92] tmpStack: [23, 31] Element taken out: 92 input: [34, 3, 98] tmpStack: [23, 31, 92] Element taken out: 98 input: [34, 3] tmpStack: [23, 31, 92, 98] Element taken out: 3 input: [34, 98, 92, 31, 23] tmpStack: [3] Element taken out: 23 input: [34, 98, 92, 31] tmpStack: [3, 23] Element taken out: 31 input: [34, 98, 92] tmpStack: [3, 23, 31] Element taken out: 92 input: [34, 98] tmpStack: [3, 23, 31, 92] Element taken out: 98 input: [34] tmpStack: [3, 23, 31, 92, 98] Element taken out: 34 input: [98, 92] tmpStack: [3, 23, 31, 34] Element taken out: 92 input: [98] tmpStack: [3, 23, 31, 34, 92] Element taken out: 98 input: [] tmpStack: [3, 23, 31, 34, 92, 98] final sorted list: [3, 23, 31, 34, 92, 98]
C++
// C++ program to sort a stack using an// auxiliary stack.#include <bits/stdc++.h>using namespace std; // This function return the sorted stackstack<int> sortStack(stack<int> &input;){ stack<int> tmpStack; while (!input.empty()) { // pop out the first element int tmp = input.top(); input.pop(); // while temporary stack is not empty and top // of stack is greater than temp while (!tmpStack.empty() && tmpStack.top() > tmp) { // pop from temporary stack and push // it to the input stack input.push(tmpStack.top()); tmpStack.pop(); } // push temp in tempory of stack tmpStack.push(tmp); } return tmpStack;} // main functionint main(){ stack<int> input; input.push(34); input.push(3); input.push(31); input.push(98); input.push(92); input.push(23); // This is the temporary stack stack<int> tmpStack = sortStack(input); cout << "Sorted numbers are:\n"; while (!tmpStack.empty()) { cout << tmpStack.top()<< " "; tmpStack.pop(); }} |
Java
// Java program to sort a stack using // a auxiliary stack.import java.util.*; class SortStack{ // This function return the sorted stack public static Stack<Integer> sortstack(Stack<Integer> input) { Stack<Integer> tmpStack = new Stack<Integer>(); while(!input.isEmpty()) { // pop out the first element int tmp = input.pop(); // while temporary stack is not empty and // top of stack is greater than temp while(!tmpStack.isEmpty() && tmpStack.peek() > tmp) { // pop from temporary stack and // push it to the input stack input.push(tmpStack.pop()); } // push temp in tempory of stack tmpStack.push(tmp); } return tmpStack; } // Driver Code public static void main(String args[]) { Stack<Integer> input = new Stack<Integer>(); input.add(34); input.add(3); input.add(31); input.add(98); input.add(92); input.add(23); // This is the temporary stack Stack<Integer> tmpStack=sortstack(input); System.out.println("Sorted numbers are:"); while (!tmpStack.empty()) { System.out.print(tmpStack.pop()+" "); } }}// This code is contributed by Danish Kaleem |
Python3
# Python program to sort a # stack using auxiliary stack. # This function return the sorted stackdef sortStack ( stack ): tmpStack = createStack() while(isEmpty(stack) == False): # pop out the first element tmp = top(stack) pop(stack) # while temporary stack is not # empty and top of stack is # greater than temp while(isEmpty(tmpStack) == False and int(top(tmpStack)) > int(tmp)): # pop from temporary stack and # push it to the input stack push(stack,top(tmpStack)) pop(tmpStack) # push temp in tempory of stack push(tmpStack,tmp) return tmpStack # Below is a complete running # program for testing above# function. # Function to create a stack. # It initializes size of stack# as 0def createStack(): stack = [] return stack # Function to check if # the stack is emptydef isEmpty( stack ): return len(stack) == 0 # Function to push an # item to stackdef push( stack, item ): stack.append( item ) # Function to get top # item of stackdef top( stack ): p = len(stack) return stack[p-1] # Function to pop an # item from stackdef pop( stack ): # If stack is empty # then error if(isEmpty( stack )): print("Stack Underflow ") exit(1) return stack.pop() # Function to print the stackdef prints(stack): for i in range(len(stack)-1, -1, -1): print(stack[i], end = ' ') print() # Driver Codestack = createStack()push( stack, str(34) )push( stack, str(3) )push( stack, str(31) )push( stack, str(98) )push( stack, str(92) )push( stack, str(23) ) print("Sorted numbers are: ")sortedst = sortStack ( stack )prints(sortedst) # This code is contributed by# Prasad Kshirsagar |
C#
// C# program to sort a stack using // a auxiliary stack. using System;using System.Collections.Generic; class GFG{// This function return the sorted stack public static Stack<int> sortstack(Stack<int> input){ Stack<int> tmpStack = new Stack<int>(); while (input.Count > 0) { // pop out the first element int tmp = input.Pop(); // while temporary stack is not empty and // top of stack is greater than temp while (tmpStack.Count > 0 && tmpStack.Peek() > tmp) { // pop from temporary stack and // push it to the input stack input.Push(tmpStack.Pop()); } // push temp in tempory of stack tmpStack.Push(tmp); } return tmpStack;} // Driver Code public static void Main(string[] args){ Stack<int> input = new Stack<int>(); input.Push(34); input.Push(3); input.Push(31); input.Push(98); input.Push(92); input.Push(23); // This is the temporary stack Stack<int> tmpStack = sortstack(input); Console.WriteLine("Sorted numbers are:"); while (tmpStack.Count > 0) { Console.Write(tmpStack.Pop() + " "); }}} // This code is contributed by Shrikant13 |
Output:
Sorted numbers are: 98 92 34 31 23 3
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