merge sort javascript code example

Example 1: merge sort javascript

// Merge Sort Implentation (Recursive)

function mergeSort (unsortedArray) {
  if (unsortedArray.length <= 1) {
    return unsortedArray;
  }
  
  const middle = Math.floor(unsortedArray.length / 2);

  const left = unsortedArray.slice(0, middle);
  const right = unsortedArray.slice(middle);

  // Using recursion to combine the left and right
  return merge(
    mergeSort(left),
    mergeSort(right)
  );
}

function merge (left, right) {
  let resultArray = [], leftIndex = 0, rightIndex = 0;

  while (leftIndex < left.length && rightIndex < right.length) {
    if (left[leftIndex] < right[rightIndex]) {
      resultArray.push(left[leftIndex]);
      leftIndex++;
    } else {
      resultArray.push(right[rightIndex]);
	  rightIndex++;
    }
  }

  return resultArray
          .concat(left.slice(leftIndex))
          .concat(right.slice(rightIndex));
}

Example 2: array sorting javascript mergesort

// Merge Sort (Recursive)
function mergeSort (unsortedArray) {
  // No need to sort the array if the array only has one element or empty
  if (unsortedArray.length <= 1) {
    return unsortedArray;
  }
  // In order to divide the array in half, we need to figure out the middle
  const middle = Math.floor(unsortedArray.length / 2);

  // This is where we will be dividing the array into left and right
  const left = unsortedArray.slice(0, middle);
  const right = unsortedArray.slice(middle);

  // Using recursion to combine the left and right
  return merge(
    mergeSort(left), mergeSort(right)
  );
}

Example 3: implement a merge sort algorithm JS

function merge(left, right) {
  const resultArray = []
  let leftIndex = 0
  let rightIndex = 0

  while (leftIndex < left.length && rightIndex < right.length) {
    if (left[leftIndex] < right[rightIndex]) {
      resultArray.push(left[leftIndex])
      leftIndex+=1
    } else {
      resultArray.push(right[rightIndex])
      rightIndex+=1
    }
  }
  return resultArray
    .concat(left.slice(leftIndex))
    .concat(right.slice(rightIndex))
}
function mergeSort(unsortedArray) {
  if (unsortedArray.length <= 1) {
    return unsortedArray;
  }
  const middle = Math.floor(unsortedArray.length / 2);
  const left = unsortedArray.slice(0, middle);
  const right = unsortedArray.slice(middle);
  return merge(
    mergeSort(left), mergeSort(right)
  );
}
mergeSort([10, 9, 8, 7, 6, 5, 4, 3, 2, 1])

Example 4: heap sort javascript

var array_length;
/* to create MAX  array */  
function heap_root(input, i) {
    var left = 2 * i + 1;
    var right = 2 * i + 2;
    var max = i;

    if (left < array_length && input[left] > input[max]) {
        max = left;
    }

    if (right < array_length && input[right] > input[max])     {
        max = right;
    }

    if (max != i) {
        swap(input, i, max);
        heap_root(input, max);
    }
}

function swap(input, index_A, index_B) {
    var temp = input[index_A];

    input[index_A] = input[index_B];
    input[index_B] = temp;
}

function heapSort(input) {
    
    array_length = input.length;

    for (var i = Math.floor(array_length / 2); i >= 0; i -= 1)      {
        heap_root(input, i);
      }

    for (i = input.length - 1; i > 0; i--) {
        swap(input, 0, i);
        array_length--;
      
      
        heap_root(input, 0);
    }
}

var arr = [3, 0, 2, 5, -1, 4, 1];
heapSort(arr);
console.log(arr);

Example 5: merge sort algorithm

/*  
    a[] is the array, p is starting index, that is 0, 
    and r is the last index of array. 
*/

#include <stdio.h>

// lets take a[5] = {32, 45, 67, 2, 7} as the array to be sorted.

// merge sort function
void mergeSort(int a[], int p, int r)
{
    int q;
    if(p < r)
    {
        q = (p + r) / 2;
        mergeSort(a, p, q);
        mergeSort(a, q+1, r);
        merge(a, p, q, r);
    }
}

// function to merge the subarrays
void merge(int a[], int p, int q, int r)
{
    int b[5];   //same size of a[]
    int i, j, k;
    k = 0;
    i = p;
    j = q + 1;
    while(i <= q && j <= r)
    {
        if(a[i] < a[j])
        {
            b[k++] = a[i++];    // same as b[k]=a[i]; k++; i++;
        }
        else
        {
            b[k++] = a[j++];
        }
    }
  
    while(i <= q)
    {
        b[k++] = a[i++];
    }
  
    while(j <= r)
    {
        b[k++] = a[j++];
    }
  
    for(i=r; i >= p; i--)
    {
        a[i] = b[--k];  // copying back the sorted list to a[]
    } 
}

// function to print the array
void printArray(int a[], int size)
{
    int i;
    for (i=0; i < size; i++)
    {
        printf("%d ", a[i]);
    }
    printf("\n");
}
 
int main()
{
    int arr[] = {32, 45, 67, 2, 7};
    int len = sizeof(arr)/sizeof(arr[0]);
 
    printf("Given array: \n");
    printArray(arr, len);
    
    // calling merge sort
    mergeSort(arr, 0, len - 1);
 
    printf("\nSorted array: \n");
    printArray(arr, len);
    return 0;
}

Example 6: javascript merge sort

const merge = (left, right) => {
  const resArr = [];
  let leftIdx = 0;
  let rightIdx = 0;

  while (leftIdx < left.length && rightIdx < right.length) {
    left[leftIdx] < right[rightIdx]
      ? resArr.push(left[leftIdx++])
      : resArr.push(right[rightIdx++]);
  }
  return [...resArr, ...left.slice(leftIdx), ...right.slice(rightIdx)];
};

const mergeSort = arr =>
  arr.length <= 1
    ? arr
    : merge(
        mergeSort(arr.slice(0, Math.floor(arr.length / 2))),
        mergeSort(arr.slice(Math.floor(arr.length / 2)))
      );