merge sort

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Imagine you have a set of numbered cards, and your task is to put them in order from smallest to largest. Now, let's say there are too many cards for you to sort them all at once. Merge Sort is like having a helper who divides the cards into smaller groups, sorts each group separately, and then combines them back together in order.

Here's how Merge Sort works step by step:

1. Divide: Your helper starts by dividing the cards into smaller groups, each containing just a few cards. They continue dividing until each group only has one card. Now, a single card is already in order!

2. Sort: Next, your helper compares the cards in each pair of groups. They arrange the cards within each pair in the correct order, from smallest to largest.

3. Merge: Finally, your helper starts combining the sorted groups back together. They take two sorted groups at a time and merge them into a single, larger sorted group. They repeat this process until all the cards are back together in one big sorted stack.

By breaking the task into smaller, manageable parts and then combining them back together, Merge Sort helps you efficiently sort a large set of cards or numbers. It's like having a team of helpers working together to organize your cards neatly!

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Source: Grepper

Tags: algorithm merge sorting whatever

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Contributed on Mar 20 2024

mrasadatik

0 Answers Avg Quality 2/10

merge sort

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This pseudocode describes the Merge Sort algorithm, which recursively divides the input array into smaller sub-arrays until each sub-array has only one element. Then, it merges these sub-arrays back together in sorted order. This algorithm maintains a time complexity of O(n log n) and uses additional space for the temporary arrays during merging, also O(n).

mergeSort(arr):
    if length of arr <= 1:
        return arr
    
    mid = length of arr / 2
    left = mergeSort(arr[0:mid])
    right = mergeSort(arr[mid:end])
    
    return merge(left, right)

merge(left, right):
    result = []
    while left is not empty and right is not empty:
        if first element of left <= first element of right:
            append first element of left to result
            remove first element from left
        else:
            append first element of right to result
            remove first element from right
    
    append remaining elements of left to result
    append remaining elements of right to result
    
    return result

Popularity 9/10 Helpfulness 3/10 Language whatever

Source: Grepper

Tags: merge merg

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Contributed on Mar 20 2024

mrasadatik

0 Answers Avg Quality 2/10

merge sort

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//merge sort
#include <iostream>

using namespace std;
void merge(int arr[],int start,int mid,int end)
{
    int n1=mid-start+1;
    int n2=end-mid;
    int l[n1],m[n2];
    for(int i=0;i<n1;i++)
    {
        l[i]=arr[start+i];
    }
    for(int j=0;j<n2;j++)
    {
        m[j]=arr[mid+1+j];
    }
    int i=0;
    int j=0;
    int k=start;
    while(i<n1&&j<n2)
    {
        if(l[i]<m[j])
        {
            arr[k]=l[i];
            k++;
            i++;
        }
        else
        {
            arr[k]=m[j];
            k++;
            j++;
        }
    }
    while(i<n1)
    {
        arr[k]=l[i];
        k++;
        i++;
    }
    while(j<n2)
    {
        arr[k]=m[j];
        k++;
        j++;
    }
}
void mergesort(int arr[],int start,int end)
{
    if(start<end)
    {
        int mid=(start+end)/2;
        mergesort(arr,start,mid);
        mergesort(arr,mid+1,end);
        merge(arr,start,mid,end);
    }
}
void display(int arr[],int n)
{
    for(int i=0;i<n;i++)
    {
        cout<<arr[i]<<" ";
    }
    cout<<endl;
}

int main()
{
    int n;
    cout<<"enter the size of the array:"<<endl;
    cin>>n;
    cout<<"enter the elements of the array:"<<endl;
    int arr[n];
    for(int i=0;i<n;i++)
    {
        cin>>arr[i];
    }
    cout<<"array as it is:"<<endl;
    display(arr,n);
    cout<<"sorted array:"<<endl;
    mergesort(arr,0,n-1);
    display(arr,n);
    return 0;
}

Popularity 10/10 Helpfulness 2/10 Language cpp

Source: Grepper

Tags: c++

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Contributed on May 27 2021

ujjwal sotra

0 Answers Avg Quality 2/10

merge sort

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// Merges two subarrays of arr[].
// First subarray is arr[l..m]
// Second subarray is arr[m+1..r]
function merge(arr, l, m, r)
{
    var n1 = m - l + 1;
    var n2 = r - m;
  
    // Create temp arrays
    var L = new Array(n1); 
    var R = new Array(n2);
  
    // Copy data to temp arrays L[] and R[]
    for (var i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for (var j = 0; j < n2; j++)
        R[j] = arr[m + 1 + j];
  
    // Merge the temp arrays back into arr[l..r]
  
    // Initial index of first subarray
    var i = 0;
    // Initial index of second subarray
    var j = 0;
    // Initial index of merged subarray
    var k = l;
  
    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) {
            arr[k] = L[i];
            i++;
        }
        else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }
  
    // Copy the remaining elements of
    // L[], if there are any
    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }
  
    // Copy the remaining elements of
    // R[], if there are any
    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }
}
  
// l for left index r is
// right index of the sub-array
// of arr to be sorted
function mergeSort(arr,l, r){
    if(l>=r){
        return;//returns recursively
    }
    var m =l+ parseInt((r-l)/2);
    mergeSort(arr,l,m);
    mergeSort(arr,m+1,r);
    merge(arr,l,m,r);
}

Popularity 10/10 Helpfulness 2/10 Language javascript

Source: sorting-algorithms.me

Tags: javascript j

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Contributed on Sep 13 2022

katanton reckless

0 Answers Avg Quality 2/10

merge sort

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this website explains merge sort well. It also has other sorts as well.
https://computerneek.org/sortingal.html

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Source: Grepper

Tags: merge merg

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Contributed on Nov 26 2022

Frantic Fox

0 Answers Avg Quality 2/10

merge sort

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<?php    
  
/* Function to merge the subarrays of a[] */  
function merge(&$a, $beg, $mid, $end)    
{    
    $n1 = ($mid - $beg) + 1;    
    $n2 = $end - $mid;    
      
   /* temporary Arrays */  
        $LeftArray = array($n1);  
        $RightArray = array($n2);  
      
    /* copy data to temp arrays */  
    for ($i = 0; $i < $n1; $i++)    
    $LeftArray[$i] = $a[$beg + $i];    
    for ($j = 0; $j < $n2; $j++)    
    $RightArray[$j] = $a[$mid + 1 + $j];    
      
    $i = 0; /* initial index of first sub-array */  
    $j = 0; /* initial index of second sub-array */   
    $k = $beg;  /* initial index of merged sub-array */  
      
    while ($i<$n1 && $j<$n2)    
    {    
        if($LeftArray[$i] <= $RightArray[$j])    
        {    
            $a[$k] = $LeftArray[$i];    
            $i++;    
        }    
        else    
        {    
            $a[$k] = $RightArray[$j];    
            $j++;    
        }    
        $k++;    
    }    
    while ($i<$n1)    
    {    
        $a[$k] = $LeftArray[$i];    
        $i++;    
        $k++;    
    }    
      
    while ($j<$n2)    
    {    
        $a[$k] = $RightArray[$j];    
        $j++;    
        $k++;    
    }    
}    
  
function mergeSort(&$a, $beg, $end)  
{  
    if ($beg < $end)   
    {  
        $mid = (int)(($beg + $end) / 2);  
        mergeSort($a, $beg, $mid);  
        mergeSort($a, $mid + 1, $end);  
        merge($a, $beg, $mid, $end);  
    }  
}  
  
/* Function to print array elements */  
    function printArray($a, $n)  
    {  
    for($i = 0; $i < $n; $i++)    
    {    
        print_r($a[$i]);    
        echo " ";    
    }        
    }  
  
    $a = array( 10, 29, 23, 6, 30, 15, 38, 40 );    
    $n = count($a);  
    echo "Before sorting array elements are - <br>";    
    printArray($a, $n);  
    mergeSort($a, 0, $n - 1);  
    echo "<br> After sorting array elements are - <br>";    
    printArray($a, $n);  
?>

Popularity 10/10 Helpfulness 2/10 Language php

Source: Grepper

Tags: merge merg

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Contributed on Mar 16 2023

Shadow

0 Answers Avg Quality 2/10

merge sort

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def mergeSort(arr):
    if len(arr) > 1:
  
         # Finding the mid of the array
        mid = len(arr)//2
  
        # Dividing the array elements
        L = arr[:mid]
  
        # into 2 halves
        R = arr[mid:]
  
        # Sorting the first half
        mergeSort(L)
  
        # Sorting the second half
        mergeSort(R)
  
        i = j = k = 0
  
        # Copy data to temp arrays L[] and R[]
        while i < len(L) and j < len(R):
            if L[i] < R[j]:
                arr[k] = L[i]
                i += 1
            else:
                arr[k] = R[j]
                j += 1
            k += 1
  
        # Checking if any element was left
        while i < len(L):
            arr[k] = L[i]
            i += 1
            k += 1
  
        while j < len(R):
            arr[k] = R[j]
            j += 1
            k += 1

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Source: Grepper

Tags: merge merg

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Contributed on Feb 17 2022

Defiant Donkey

0 Answers Avg Quality 2/10

merge sort

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//recursive merge sort

	public static void mergeSort(int[] a){
		mergeSort(a, 0, a.length-1);
	}

	private static void mergeSort(int[] a, int i, int j){
		if (i == j)
			return;
		int mid = (i + j)/2;
		mergeSort(a, i, mid);
		mergeSort(a, mid + 1, j);
		merge(a, i, j);
	}

	private static void merge(int[] a, int i, int j){
		int[] temp = new int[j - i + 1];
		int mid = (i + j)/2;
		int left = i, right = mid + 1, k = 0;
		while (left <= mid && right <= j && k < temp.length){
			if (a[left] < a[right])
				temp[k++] = a[left++];
			else
				temp[k++] = a[right++];
		}
		while (left <= mid)
			temp[k++] = a[left++];
		while (right <= j)
			temp[k++] = a[right++];

		for (int m = 0; m < temp.length; m++)
			a[i + m] = temp[m];
	}

Popularity 10/10 Helpfulness 2/10 Language java

Source: Grepper

Tags: java

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Contributed on Apr 17 2022

Dovi91

0 Answers Avg Quality 2/10

Merge Sort

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<script>
  
// JavaScript program for Merge Sort
  
// Merges two subarrays of arr[].
// First subarray is arr[l..m]
// Second subarray is arr[m+1..r]
function merge(arr, l, m, r)
{
    var n1 = m - l + 1;
    var n2 = r - m;
  
    // Create temp arrays
    var L = new Array(n1); 
    var R = new Array(n2);
  
    // Copy data to temp arrays L[] and R[]
    for (var i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for (var j = 0; j < n2; j++)
        R[j] = arr[m + 1 + j];
  
    // Merge the temp arrays back into arr[l..r]
  
    // Initial index of first subarray
    var i = 0;
  
    // Initial index of second subarray
    var j = 0;
  
    // Initial index of merged subarray
    var k = l;
  
    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) {
            arr[k] = L[i];
            i++;
        }
        else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }
  
    // Copy the remaining elements of
    // L[], if there are any
    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }
  
    // Copy the remaining elements of
    // R[], if there are any
    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }
}
  
// l is for left index and r is
// right index of the sub-array
// of arr to be sorted */
function mergeSort(arr,l, r){
    if(l>=r){
        return;//returns recursively
    }
    var m =l+ parseInt((r-l)/2);
    mergeSort(arr,l,m);
    mergeSort(arr,m+1,r);
    merge(arr,l,m,r);
}
  
// UTILITY FUNCTIONS
// Function to print an array
function printArray( A, size)
{
    for (var i = 0; i < size; i++)
       document.write(  A[i] + " ");
}
  
  
var arr = [ 12, 11, 13, 5, 6, 7 ];
    var arr_size = arr.length;
  
    document.write(  "Given array is <br>");
    printArray(arr, arr_size);
  
    mergeSort(arr, 0, arr_size - 1);
  
    document.write( "<br>Sorted array is <br>");
    printArray(arr, arr_size);
  
// This code is contributed by SoumikMondal
  
</script>

Popularity 10/10 Helpfulness 1/10 Language javascript

Source: www.geeksforgeeks.org

Tags: javascript j

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Contributed on May 20 2022

Sayyed Aaman

0 Answers Avg Quality 2/10

merge sort

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<?php

/* Function to merge the subarrays of a[] */
function merge(&$a, $beg, $mid, $end)
{
    $n1 = ($mid - $beg) + 1;
    $n2 = $end - $mid;

    /* temporary Arrays */
    $LeftArray  = [$n1];
    $RightArray = [$n2];

    /* copy data to temp arrays */
    for ($i = 0; $i < $n1; $i++) {
        $LeftArray[$i] = $a[$beg + $i];
    }
    for ($j = 0; $j < $n2; $j++) {
        $RightArray[$j] = $a[$mid + 1 + $j];
    }

    $i = 0; /* initial index of first sub-array */
    $j = 0; /* initial index of second sub-array */
    $k = $beg;  /* initial index of merged sub-array */

    while ($i < $n1 && $j < $n2) {
        if ($LeftArray[$i] <= $RightArray[$j]) {
            $a[$k] = $LeftArray[$i];
            $i++;
        } else {
            $a[$k] = $RightArray[$j];
            $j++;
        }
        $k++;
    }
    while ($i < $n1) {
        $a[$k] = $LeftArray[$i];
        $i++;
        $k++;
    }

    while ($j < $n2) {
        $a[$k] = $RightArray[$j];
        $j++;
        $k++;
    }
}

function mergeSort(&$a, $beg, $end)
{
    if ($beg < $end) {
        $mid = (int)(($beg + $end) / 2);
        mergeSort($a, $beg, $mid);
        mergeSort($a, $mid + 1, $end);
        merge($a, $beg, $mid, $end);
    }
}

/* Function to print array elements */
function printArray($a, $n)
{
    for ($i = 0; $i < $n; $i++) {
        print_r($a[$i]);
        echo " ";
    }
}

$a = [10, 29, 23, 6, 30, 15, 38, 40];
$n = count($a);
echo "Before sorting array elements are - <br>";
printArray($a, $n);
mergeSort($a, 0, $n - 1);
echo "<br> After sorting array elements are - <br>";
printArray($a, $n);
?>

Popularity 9/10 Helpfulness 1/10 Language php

Source: Grepper

Tags: merge php

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Contributed on Mar 16 2023

Shadow

0 Answers Avg Quality 2/10

merge sort

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1

/* Java program for Merge Sort */
class MergeSort
{
    // Merges two subarrays of arr[].
    // First subarray is arr[l..m]
    // Second subarray is arr[m+1..r]
    void merge(int arr[], int l, int m, int r)
    {
        // Find sizes of two subarrays to be merged
        int n1 = m - l + 1;
        int n2 = r - m;
 
        /* Create temp arrays */
        int L[] = new int[n1];
        int R[] = new int[n2];
 
        /*Copy data to temp arrays*/
        for (int i = 0; i < n1; ++i)
            L[i] = arr[l + i];
        for (int j = 0; j < n2; ++j)
            R[j] = arr[m + 1 + j];
 
        /* Merge the temp arrays */
 
        // Initial indexes of first and second subarrays
        int i = 0, j = 0;
 
        // Initial index of merged subarray array
        int k = l;
        while (i < n1 && j < n2) {
            if (L[i] <= R[j]) {
                arr[k] = L[i];
                i++;
            }
            else {
                arr[k] = R[j];
                j++;
            }
            k++;
        }
 
        /* Copy remaining elements of L[] if any */
        while (i < n1) {
            arr[k] = L[i];
            i++;
            k++;
        }
 
        /* Copy remaining elements of R[] if any */
        while (j < n2) {
            arr[k] = R[j];
            j++;
            k++;
        }
    }
 
    // Main function that sorts arr[l..r] using
    // merge()
    void sort(int arr[], int l, int r)
    {
        if (l < r) {
            // Find the middle point
            int m =l+ (r-l)/2;
 
            // Sort first and second halves
            sort(arr, l, m);
            sort(arr, m + 1, r);
 
            // Merge the sorted halves
            merge(arr, l, m, r);
        }
    }
 
    /* A utility function to print array of size n */
    static void printArray(int arr[])
    {
        int n = arr.length;
        for (int i = 0; i < n; ++i)
            System.out.print(arr[i] + " ");
        System.out.println();
    }
 
    // Driver code
    public static void main(String args[])
    {
        int arr[] = { 12, 11, 13, 5, 6, 7 };
 
        System.out.println("Given Array");
        printArray(arr);
 
        MergeSort ob = new MergeSort();
        ob.sort(arr, 0, arr.length - 1);
 
        System.out.println("\nSorted array");
        printArray(arr);
    }
}
/* This code is contributed by Rajat Mishra */

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Source: www.geeksforgeeks.org

Tags: merge merg

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Contributed on Jun 08 2022

Pankaj Kumar Prasad

0 Answers Avg Quality 2/10

merge sort

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