quick 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: javascript quicksort

const quicksort = arr =>
  arr.length <= 1
    ? arr
    : [
        ...quicksort(arr.slice(1).filter((el) => el < arr[0])),
        arr[0],
        ...quicksort(arr.slice(1).filter((el) => el >= arr[0])),
      ];

Example 3: quick sort in javascript

function quicksort(array) {
  if (array.length <= 1) {
    return array;
  }

  var pivot = array[0];
  
  var left = []; 
  var right = [];

  for (var i = 1; i < array.length; i++) {
    array[i] < pivot ? left.push(array[i]) : right.push(array[i]);
  }

  return quicksort(left).concat(pivot, quicksort(right));
};

Example 4: quicksort javascript

const quickSort = array =>
  (function qsort(arr, start, end) {
    if (start >= end) return arr;
    let swapPos = start;

    for (let i = start; i <= end; i++) {
      if (arr[i] <= arr[end]) {
        [arr[swapPos], arr[i]] = [arr[i], arr[swapPos]];
        swapPos++;
      }
    }
    qsort(arr, start, --swapPos - 1);
    qsort(arr, swapPos + 1, end);

    return arr;
  })(Array.from(array), 0, array.length - 1);

Example 5: Insertion Sort javascript

const insertionSort = (inputArr) => {
  const {length} = inputArr;
  const retArray = inputArr;
  for (let i = 1; i < length; i++) {
    const key = inputArr[i];
    let j = i - 1;
    while (j >= 0 && inputArr[j] > key) {
      retArray[j + 1] = inputArr[j];
      j -= 1;
    }
    retArray[j + 1] = key;
  }
  return retArray;
};
insertionSort([10, 9, 8, 7, 6, 5, 4, 3, 2, 1])

Example 6: quick sort js

var items = [5, 3, 7, 6, 2, 9];

function swap(items, leftIndex, rightIndex) {
  var temp = items[leftIndex];
  items[leftIndex] = items[rightIndex];
  items[rightIndex] = temp;
}

function partition(items, left, right) {
  var pivot = items[Math.floor((right + left) / 2)], //middle element
    i = left, //left pointer
    j = right; //right pointer
  while (i <= j) {
    while (items[i] < pivot) {
      i++;
    }
    while (items[j] > pivot) {
      j--;
    }
    if (i <= j) {
      swap(items, i, j); //sawpping two elements
      i++;
      j--;
    }
  }
  return i;
}

function quickSort(items, left, right) {
  var index;
  if (items.length > 1) {
    index = partition(items, left, right); //index returned from partition
    if (left < index - 1) {
      //more elements on the left side of the pivot
      quickSort(items, left, index - 1);
    }
    if (index < right) {
      //more elements on the right side of the pivot
      quickSort(items, index, right);
    }
  }
  return items;
}

// first call to quick sort
var sortedArray = quickSort(items, 0, items.length - 1);
console.log(sortedArray); //prints [2,3,5,6,7,9]