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 tempory 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 function int 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(); } } |
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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 tempory 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) |
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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 tempory 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) |
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Output:
Sorted and merged stack : 34 31 23 12 3 1
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