Merging and Sorting Two Unsorted Stacks
Given 2 input stacks with elements in an unsorted manner. Problem is to merge them into a new final stack, such that the elements become arranged in a sorted manner.
Examples:
Input : s1 : 9 4 2 1
s2: 8 17 3 10
Output : final stack: 1 2 3 4 8 9 10 17
Input : s1 : 5 7 2 6 4
s2 : 12 9 3
Output : final stack: 2 3 4 5 6 7 9 12
Create an empty stack to store result. We first insert elements of both stacks into the result. Then we sort the result stack.
C++
// C++ program to merge to unsorted stacks// into a third stack in sorted way.#include <bits/stdc++.h>using namespace std;// Sorts input stack and returns sorted stack.stack<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 temporary of stack tmpStack.push(tmp); } return tmpStack;}stack<int> sortedMerge(stack<int>& s1, stack<int>& s2){ // Push contents of both stacks in result stack<int> res; while (!s1.empty()) { res.push(s1.top()); s1.pop(); } while (!s2.empty()) { res.push(s2.top()); s2.pop(); } // Sort the result stack. return sortStack(res);}// main functionint main(){ stack<int> s1, s2; s1.push(34); s1.push(3); s1.push(31); s2.push(1); s2.push(12); s2.push(23); // This is the temporary stack stack<int> tmpStack = sortedMerge(s1, s2); cout << "Sorted and merged stack :\n"; while (!tmpStack.empty()) { cout << tmpStack.top() << " "; tmpStack.pop(); }} |
Java
// Java program to merge to unsorted stacks// into a third stack in sorted way.import java.io.*;import java.util.*;public class GFG { // This is the temporary stack static Stack<Integer> res = new Stack<Integer>(); static Stack<Integer> tmpStack = new Stack<Integer>(); // Sorts input stack and returns // sorted stack. static void sortStack(Stack<Integer> input) { while (input.size() != 0) { // pop out the first element int tmp = input.peek(); input.pop(); // while temporary stack is not empty and // top of stack is greater than temp while (tmpStack.size() != 0 && tmpStack.peek() > tmp) { // pop from temporary stack and push // it to the input stack input.push(tmpStack.peek()); tmpStack.pop(); } // push temp in temporary of stack tmpStack.push(tmp); } } static void sortedMerge(Stack<Integer> s1, Stack<Integer> s2) { // Push contents of both stacks in result while (s1.size() != 0) { res.push(s1.peek()); s1.pop(); } while (s2.size() != 0) { res.push(s2.peek()); s2.pop(); } // Sort the result stack. sortStack(res); } // main function public static void main(String args[]) { Stack<Integer> s1 = new Stack<Integer>(); Stack<Integer> s2 = new Stack<Integer>(); s1.push(34); s1.push(3); s1.push(31); s2.push(1); s2.push(12); s2.push(23); sortedMerge(s1, s2); System.out.println("Sorted and merged stack :"); while (tmpStack.size() != 0) { System.out.print(tmpStack.peek() + " "); tmpStack.pop(); } }}// This code is contributed by Manish Shaw// (manishshaw1) |
Python3
# Python3 program to merge to unsorted stacks# into a third stack in sorted way.# Sorts input stack and returns# sorted stack.def sortStack(Input): tmpStack = [] while len(Input) != 0: # pop out the first element tmp = Input[-1] Input.pop() # while temporary stack is not empty and # top of stack is greater than temp while len(tmpStack) != 0 and tmpStack[-1] > tmp: # pop from temporary stack and push # it to the input stack Input.append(tmpStack[-1]) tmpStack.pop() # push temp in temporary of stack tmpStack.append(tmp) return tmpStack def sortedMerge(s1, s2): # Push contents of both stacks in result res = [] while len(s1) !=0 : res.append(s1[-1]) s1.pop() while len(s2) !=0 : res.append(s2[-1]) s2.pop() # Sort the result stack. return sortStack(res)s1 = []s2 = []s1.append(34)s1.append(3)s1.append(31)s2.append(1)s2.append(12)s2.append(23)# This is the temporary stacktmpStack = []tmpStack = sortedMerge(s1, s2)print("Sorted and merged stack :")while len(tmpStack) != 0 : print(tmpStack[-1], end = " ") tmpStack.pop() # This code is contributed by decode2207. |
C#
// C# program to merge to unsorted stacks// into a third stack in sorted way.using System;using System.Collections.Generic;class GFG { // Sorts input stack and returns // sorted stack. static Stack<int> sortStack(ref Stack<int> input) { Stack<int> tmpStack = new Stack<int>(); while (input.Count != 0) { // pop out the first element int tmp = input.Peek(); 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.Peek()); tmpStack.Pop(); } // push temp in temporary of stack tmpStack.Push(tmp); } return tmpStack; } static Stack<int> sortedMerge(ref Stack<int> s1, ref Stack<int> s2) { // Push contents of both stacks in result Stack<int> res = new Stack<int>(); while (s1.Count!=0) { res.Push(s1.Peek()); s1.Pop(); } while (s2.Count!=0) { res.Push(s2.Peek()); s2.Pop(); } // Sort the result stack. return sortStack(ref res); } // main function static void Main() { Stack<int> s1 = new Stack<int>(); Stack<int> s2 = new Stack<int>(); s1.Push(34); s1.Push(3); s1.Push(31); s2.Push(1); s2.Push(12); s2.Push(23); // This is the temporary stack Stack<int> tmpStack = new Stack<int>(); tmpStack = sortedMerge(ref s1,ref s2); Console.Write("Sorted and merged stack :\n"); while (tmpStack.Count!=0) { Console.Write(tmpStack.Peek() + " "); tmpStack.Pop(); } }}// This code is contributed by Manish Shaw// (manishshaw1) |
Javascript
<script> // Javascript program to merge to unsorted stacks // into a third stack in sorted way. // This is the temporary stack let res = []; let tmpStack = []; // Sorts input stack and returns // sorted stack. function sortStack(input) { while (input.length != 0) { // pop out the first element let tmp = input[input.length - 1]; input.pop(); // while temporary stack is not empty and // top of stack is greater than temp while (tmpStack.length != 0 && tmpStack[tmpStack.length - 1] > tmp) { // pop from temporary stack and push // it to the input stack input.push(tmpStack[tmpStack.length - 1]); tmpStack.pop(); } // push temp in temporary of stack tmpStack.push(tmp); } } function sortedMerge(s1, s2) { // Push contents of both stacks in result while (s1.length != 0) { res.push(s1[s1.length - 1]); s1.pop(); } while (s2.length != 0) { res.push(s2[s2.length - 1]); s2.pop(); } // Sort the result stack. sortStack(res); } let s1 = []; let s2 = []; s1.push(34); s1.push(3); s1.push(31); s2.push(1); s2.push(12); s2.push(23); sortedMerge(s1, s2); document.write("Sorted and merged stack :" + "</br>"); while (tmpStack.length != 0) { document.write(tmpStack[tmpStack.length - 1] + " "); tmpStack.pop(); } // This code is contributed by divyesh072019.</script> |
Output:
Sorted and merged stack : 34 31 23 12 3 1
Time Complexity: O((n+m)2) where n and m are number of elements in both the stacks respectively.
Auxiliary Space: O(n+m)
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