Quick sort

.eslintrc.json

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+{
+    "env": {
+      "browser": true,
+      "node": true,
+      "commonjs": true,
+      "jest": true,
+      "es6": true
+    },
+    "globals": {
+      "err": true,
+      "req": true,
+      "res": true,
+      "next": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+      "sourceType": "module"
+    },
+    "rules": {
+      "no-console": "off",
+      "indent": [ "error", 2 ],
+      "quotes": ["error", "single", { "allowTemplateLiterals": true }],
+      "comma-dangle": ["error", "always-multiline"],
+      "semi": [ "error", "always" ]
+    }
+  }
+

BLOG.md

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+# Quick Sort 
+
+ Divide and Conquer algorithm. It picks an element as pivot and partitions the given array around the picked pivot
+
+
+## Trace :
+
+Sample Array : [8,4,23,42,16,15] 
+
+![passes](p1.jpg)
+

challanges/quickSort/quickSort.js

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+'use strict';
+function swap(arr, leftIndex, rightIndex){
+  let temp = arr[leftIndex];
+  //   console.log('temp' , temp);
+  //   console.log('left' , arr[leftIndex]);
+
+  arr[leftIndex] = arr[rightIndex];
+  //   console.log('left after' , arr[leftIndex]);
+  //   console.log('right' , arr[rightIndex]);
+
+  arr[rightIndex] = temp;
+  //   console.log('right after' , arr[rightIndex]);
+
+}
+function partition(arr, leftIdx, rightIdx) {
+  let pivot   = arr[Math.floor((rightIdx + leftIdx) / 2)], 
+    i       = leftIdx, 
+    j       = rightIdx; 
+  console.log('pivot' ,pivot);
+  while (i <= j) {
+    while (arr[i] < pivot) {
+      i++;
+
+    }
+    while (arr[j] > pivot) {
+      j--;
+    }
+    if (i <= j) {
+      swap(arr, i, j); 
+      i++;
+      j--;
+    }
+  }
+  return i;
+}
+
+function quickSort(arr, leftIdx, rightIdx) {
+  let index;
+  if (arr.length > 1) {
+    index = partition(arr, leftIdx, rightIdx); 
+    console.log('left',leftIdx);
+    console.log('index',index);
+    console.log('right',rightIdx);
+    console.log('arr' ,arr);
+
+
+    if (leftIdx < index - 1) { 
+      quickSort(arr, leftIdx, index - 1);
+    }
+    if (index < rightIdx) {
+      quickSort(arr, index, rightIdx);
+    }
+  }
+  return arr;
+}
+
+let arr = [8,4,23,42,16,15];
+quickSort(arr, 0, arr.length - 1);
+console.log(quickSort(arr, 0, arr.length - 1)); 
+module.exports = quickSort ;
+// used 'https://www.guru99.com/quicksort-in-javascript.html' for solving this code challange 

challanges/quickSort/quickSort.test.js

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+
+'use strict';
+// eslint-disable-next-line no-unused-vars
+const quickSort = require('./quickSort.js');
+
+describe(`quick sort`, () => {
+
+  it('sort an array', () => {
+    const arr = [5,2,8,4,6,7];
+    expect(quickSort(arr, 0, arr.length-1)).toEqual([2,4,5,6,7,8]);
+  });
+
+  it(' sort an array with duplicate values', () => {
+    const arr = [5,2,8,4,6,7,6];
+    expect(quickSort(arr, 0, arr.length-1)).toEqual([2,4,5,6,6,7,8]);
+  });
+
+});