Merge two sorted arrays using Priority queue
Last Updated :
23 Jul, 2025
Given two sorted arrays A[] and B[] of sizes N and M respectively, the task is to merge them in a sorted manner.
Examples:
Input: A[] = { 5, 6, 8 }, B[] = { 4, 7, 8 }
Output: 4 5 6 7 8 8
Input: A[] = {1, 3, 4, 5}, B] = {2, 4, 6, 8}
Output: 1 2 3 4 4 5 6 8
Input: A[] = {5, 8, 9}, B[] = {4, 7, 8}
Output: 4 5 7 8 8 9
Approach: The given problem, merging two sorted arrays using minheap already exists. But here the idea is to use a priority_queue to implement min-heap provided by STL. Follow the steps below to solve the problem:
Below is the implementation of the above approach:
C++
// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;
// Function to merge two arrays
void merge(int A[], int B[], int N, int M)
{
// Stores the merged array
int res[N + M];
// Create a min priority_queue
priority_queue<int, vector<int>, greater<int> > pq;
// Traverse the array A[]
for (int i = 0; i < N; i++)
pq.push(A[i]);
// Traverse the array B[]
for (int i = 0; i < M; i++)
pq.push(B[i]);
int j = 0;
// Iterate until the
// pq is not empty
while (!pq.empty()) {
// Stores the top element
// of pq into res[j]
res[j++] = pq.top();
// Removes the top element
pq.pop();
}
// Print the merged array
for (int i = 0; i < N + M; i++)
cout << res[i] << ' ';
}
// Driver Code
int main()
{
// Input
int A[] = { 5, 6, 8 };
int B[] = { 4, 7, 8 };
int N = sizeof(A) / sizeof(A[0]);
int M = sizeof(B) / sizeof(B[0]);
// Function call
merge(A, B, N, M);
return 0;
}
// Java program for the above approach
import java.util.*;
class GFG{
// Function to merge two arrays
static void merge(int A[], int B[], int N, int M)
{
// Stores the merged array
int []res = new int[N + M];
// Create a min priority_queue
Queue<Integer> pq = new PriorityQueue<>();
// Traverse the array A[]
for(int i = 0; i < N; i++)
pq.add(A[i]);
// Traverse the array B[]
for(int i = 0; i < M; i++)
pq.add(B[i]);
int j = 0;
// Iterate until the
// pq is not empty
while (!pq.isEmpty())
{
// Stores the top element
// of pq into res[j]
res[j++] = pq.peek();
// Removes the top element
pq.remove();
}
// Print the merged array
for(int i = 0; i < N + M; i++)
System.out.print(res[i] + " ");
}
// Driver Code
public static void main(String[] args)
{
// Input
int A[] = { 5, 6, 8 };
int B[] = { 4, 7, 8 };
int N = A.length;
int M = B.length;
// Function call
merge(A, B, N, M);
}
}
// This code is contributed by todaysgaurav
# Python3 program for the above approach
from queue import PriorityQueue
# Function to merge two arrays
def merge(A, B, N, M):
# Stores the merged array
res = [0 for i in range(N + M)]
# Create a min priority_queue
pq = PriorityQueue()
# Traverse the array A[]
for i in range(N):
pq.put(A[i])
# Traverse the array B[]
for i in range(M):
pq.put(B[i])
j = 0
# Iterate until the
# pq is not empty
while not pq.empty():
# Removes the top element and
# stores it into res[j]
res[j] = pq.get()
j += 1
# Print the merged array
for i in range(N + M):
print(res[i], end = " ")
# return back to main
return
# Driver code
if __name__ == '__main__':
# Input
A = [ 5, 6, 8 ]
B = [ 4, 7, 8 ]
N = len(A)
M = len(B)
# Function call
merge(A, B, N, M)
# This code is contributed by MuskanKalra1
// C# program for the above approach.
using System;
using System.Collections.Generic;
public class GFG {
public static int cmp(int a, int b) { return a - b; }
// Function to merge two arrays
static void merge(int[] A, int[] B, int N, int M)
{
// Stores the merged array
int[] res = new int[N + M];
// Create a min priority_queue using List and cmp
// comparator
List<int> pq = new List<int>();
// Traverse the array A[]
for (int i = 0; i < N; i++)
pq.Add(A[i]);
// Traverse the array B[]
for (int i = 0; i < M; i++)
pq.Add(B[i]);
int j = 0;
pq.Sort(cmp);
// Iterate until the
// pq is not empty
int index = 0;
while (index < pq.Count) {
// Stores the top element
// of pq into res[j]
res[j++] = pq[index];
// Removes the top element
index++;
}
// Print the merged array
for (int i = 0; i < N + M; i++)
Console.Write(res[i] + " ");
}
public static void Main(string[] args)
{
// Input
int[] A = { 5, 6, 8 };
int[] B = { 4, 7, 8 };
int N = A.Length;
int M = B.Length;
// Function call
merge(A, B, N, M);
}
}
// This code is contributed by adityamaharshi21.
<script>
// Javascript program for the above approach
// Function to merge two arrays
function merge(A, B, N, M)
{
// Stores the merged array
var res = Array(N+M).fill(0);
// Create a min priority_queue
var pq = [];
// Traverse the array A[]
for (var i = 0; i < N; i++)
pq.push(A[i]);
// Traverse the array B[]
for (var i = 0; i < M; i++)
pq.push(B[i]);
var j = 0;
pq.sort((a,b)=>b-a);
// Iterate until the
// pq is not empty
while (pq.length!=0) {
// Stores the top element
// of pq into res[j]
res[j++] = pq[pq.length-1];
// Removes the top element
pq.pop();
pq.sort((a,b)=>b-a);
}
// Print the merged array
for (var i = 0; i < N + M; i++)
document.write(res[i] + ' ');
}
// Driver Code
// Input
var A = [5, 6, 8];
var B = [4, 7, 8];
var N = A.length;
var M = B.length;
// Function call
merge(A, B, N, M);
// This code is contributed by rrrtnx.
</script>
Time Complexity: O((N+M)*log(N+M))
Auxiliary Space: O(N+M)
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