Sort an array when two halves are sorted
Last Updated :
23 Jun, 2023
Given an integer array of which both first half and second half are sorted. Task is to merge two sorted halves of array into single sorted array.
Examples:
Input : A[] = { 2, 3, 8, -1, 7, 10 }
Output : -1, 2, 3, 7, 8, 10
Input : A[] = {-4, 6, 9, -1, 3 }
Output : -4, -1, 3, 6, 9
Method 1: A Simple Solution is to sort the array using built in functions (generally an implementation of quick sort).
Below is the implementation of above method:
C++
#include <bits/stdc++.h>
using namespace std;
void mergeTwoHalf(int A[], int n)
{
sort(A, A + n);
}
int main()
{
int A[] = { 2, 3, 8, -1, 7, 10 };
int n = sizeof(A) / sizeof(A[0]);
mergeTwoHalf(A, n);
for (int i = 0; i < n; i++)
cout << A[i] << " ";
return 0;
}
|
Java
import java.io.*;
import java.util.*;
class GFG {
static void mergeTwoHalf(int[] A, int n)
{
Arrays.sort(A);
}
static public void main(String[] args)
{
int[] A = { 2, 3, 8, -1, 7, 10 };
int n = A.length;
mergeTwoHalf(A, n);
for (int i = 0; i < n; i++)
System.out.print(A[i] + " ");
}
}
|
Python3
def mergeTwoHalf(A, n):
A.sort()
if __name__ == '__main__':
A = [2, 3, 8, -1, 7, 10]
n = len(A)
mergeTwoHalf(A, n)
for i in range(n):
print(A[i], end=" ")
|
C#
using System;
class GFG {
static void mergeTwoHalf(int[] A, int n)
{
Array.Sort(A);
}
static public void Main()
{
int[] A = { 2, 3, 8, -1, 7, 10 };
int n = A.Length;
mergeTwoHalf(A, n);
for (int i = 0; i < n; i++)
Console.Write(A[i] + " ");
}
}
|
PHP
<?php
function mergeTwoHalf(&$A, $n)
{
sort($A, 0);
}
$A = array(2, 3, 8, -1, 7, 10);
$n = sizeof($A);
mergeTwoHalf($A, $n);
for ($i = 0; $i < $n; $i++)
echo $A[$i] . " ";
?>
|
Javascript
<script>
function mergeTwoHalf(A, n)
{
A.sort((a,b) => a-b);
}
var A = [ 2, 3, 8, -1, 7, 10 ];
var n = A.length;
mergeTwoHalf(A, n);
for (var i = 0; i < n; i++)
document.write( A[i] + " ");
</script>
|
Time Complexity: 
best & average case, 
worst case (for quicksort)
Space Complexity: 
to 
depending on the case & implementation (for quicksort)
For more details, check out the GFG article on Quicksort.
Method 2: A more efficient solution is to use an auxiliary array which is very similar to the Merge Function of Merge sort.
Below is the implementation of above approach :
C++
#include <bits/stdc++.h>
using namespace std;
void mergeTwoHalf(int A[], int n)
{
int half_i = 0;
int temp[n];
for (int i = 0; i < n - 1; i++) {
if (A[i] > A[i + 1]) {
half_i = i + 1;
break;
}
}
if (half_i == 0)
return;
int i = 0, j = half_i, k = 0;
while (i < half_i && j < n) {
if (A[i] < A[j])
temp[k++] = A[i++];
else
temp[k++] = A[j++];
}
while (i < half_i)
temp[k++] = A[i++];
while (j < n)
temp[k++] = A[j++];
for (int i = 0; i < n; i++)
A[i] = temp[i];
}
int main()
{
int A[] = { 2, 3, 8, -1, 7, 10 };
int n = sizeof(A) / sizeof(A[0]);
mergeTwoHalf(A, n);
for (int i = 0; i < n; i++)
cout << A[i] << " ";
return 0;
}
|
Java
import java.io.*;
class GFG {
static void mergeTwoHalf(int[] A, int n)
{
int half_i = 0;
int i;
int[] temp = new int[n];
for (i = 0; i < n - 1; i++) {
if (A[i] > A[i + 1]) {
half_i = i + 1;
break;
}
}
if (half_i == 0)
return;
i = 0;
int j = half_i;
int k = 0;
while (i < half_i && j < n) {
if (A[i] < A[j])
temp[k++] = A[i++];
else
temp[k++] = A[j++];
}
while (i < half_i)
temp[k++] = A[i++];
while (j < n)
temp[k++] = A[j++];
for (i = 0; i < n; i++)
A[i] = temp[i];
}
static public void main(String[] args)
{
int[] A = { 2, 3, 8, -1, 7, 10 };
int n = A.length;
mergeTwoHalf(A, n);
for (int i = 0; i < n; i++)
System.out.print(A[i] + " ");
}
}
|
Python3
def mergeTwoHalf(A, n):
half_i = 0
temp = [0 for i in range(n)]
for i in range(n - 1):
if (A[i] > A[i + 1]):
half_i = i + 1
break
if (half_i == 0):
return
i = 0
j = half_i
k = 0
while (i < half_i and j < n):
if (A[i] < A[j]):
temp[k] = A[i]
k += 1
i += 1
else:
temp[k] = A[j]
k += 1
j += 1
while i < half_i:
temp[k] = A[i]
k += 1
i += 1
while (j < n):
temp[k] = A[j]
k += 1
j += 1
for i in range(n):
A[i] = temp[i]
A = [ 2, 3, 8, -1, 7, 10 ]
n = len(A)
mergeTwoHalf(A, n)
print(*A, sep = ' ')
|
C#
using System
class GFG {
static void mergeTwoHalf(int[] A, int n)
{
int half_i = 0
int i
int[] temp
= new int[n]
for (i = 0 i < n - 1 i++)
{
if (A[i] > A[i + 1]) {
half_i = i + 1 break
}
}
if (half_i == 0)
return
i = 0 int j = half_i int k
= 0 while (i < half_i & &j < n)
{
if (A[i] < A[j])
temp[k++] = A[i++] else temp[k++]
= A[j++]
}
while (i < half_i)
temp[k++] = A[i++]
while (j < n) temp[k++]
= A[j++]
for (i = 0 i < n i++) A[i]
= temp[i]
}
static public void Main()
{
int[] A
= { 2,
3,
8,
-1,
7,
10 } int n
= A.Length mergeTwoHalf(A, n)
for (int i = 0 i < n i++)
Console.Write(A[i] + " ")
}
}
|
Javascript
<script>
function mergeTwoHalf(A, n)
{
let half_i = 0;
let temp = new Array(n);
temp.fill(0);
for (let i = 0; i < n - 1; i++) {
if (A[i] > A[i + 1]) {
half_i = i + 1;
break;
}
}
if (half_i == 0)
return;
let i = 0, j = half_i, k = 0;
while (i < half_i && j < n) {
if (A[i] < A[j])
temp[k++] = A[i++];
else
temp[k++] = A[j++];
}
while (i < half_i)
temp[k++] = A[i++];
while (j < n)
temp[k++] = A[j++];
for (let i = 0; i < n; i++)
A[i] = temp[i];
}
let A = [ 2, 3, 8, -1, 7, 10 ];
let n = A.length;
mergeTwoHalf(A, n);
for (let i = 0; i < n; i++)
document.write(A[i] + " ");
</script>
|
Time Complexity: 
Space Complexity:
Reference: https://www.careercup.com/question?id=8412257
Similar Reads
Sorting Algorithms
A Sorting Algorithm is used to rearrange a given array or list of elements in an order. For example, a given array [10, 20, 5, 2] becomes [2, 5, 10, 20] after sorting in increasing order and becomes [20, 10, 5, 2] after sorting in decreasing order. There exist different sorting algorithms for differ
3 min read
Introduction to Sorting Techniques – Data Structure and Algorithm Tutorials
Sorting refers to rearrangement of a given array or list of elements according to a comparison operator on the elements. The comparison operator is used to decide the new order of elements in the respective data structure. Why Sorting Algorithms are ImportantThe sorting algorithm is important in Com
3 min read
Most Common Sorting Algorithms
Selection Sort
Selection Sort is a comparison-based sorting algorithm. It sorts an array by repeatedly selecting the smallest (or largest) element from the unsorted portion and swapping it with the first unsorted element. This process continues until the entire array is sorted. First we find the smallest element a
8 min read
Bubble Sort Algorithm
Bubble Sort is the simplest sorting algorithm that works by repeatedly swapping the adjacent elements if they are in the wrong order. This algorithm is not suitable for large data sets as its average and worst-case time complexity are quite high. We sort the array using multiple passes. After the fi
8 min read
Insertion Sort Algorithm
Insertion sort is a simple sorting algorithm that works by iteratively inserting each element of an unsorted list into its correct position in a sorted portion of the list. It is like sorting playing cards in your hands. You split the cards into two groups: the sorted cards and the unsorted cards. T
9 min read
Merge Sort - Data Structure and Algorithms Tutorials
Merge sort is a popular sorting algorithm known for its efficiency and stability. It follows the divide-and-conquer approach. It works by recursively dividing the input array into two halves, recursively sorting the two halves and finally merging them back together to obtain the sorted array. How do
14 min read
Quick Sort
QuickSort is a sorting algorithm based on the Divide and Conquer that picks an element as a pivot and partitions the given array around the picked pivot by placing the pivot in its correct position in the sorted array. It works on the principle of divide and conquer, breaking down the problem into s
13 min read
Heap Sort - Data Structures and Algorithms Tutorials
Heap sort is a comparison-based sorting technique based on Binary Heap Data Structure. It can be seen as an optimization over selection sort where we first find the max (or min) element and swap it with the last (or first). We repeat the same process for the remaining elements. In Heap Sort, we use
14 min read
Counting Sort - Data Structures and Algorithms Tutorials
Counting Sort is a non-comparison-based sorting algorithm. It is particularly efficient when the range of input values is small compared to the number of elements to be sorted. The basic idea behind Counting Sort is to count the frequency of each distinct element in the input array and use that info
9 min read