QuickSort added

Author: soumyadip007

Sorting/QuickSort.ipynb

@@ -2,7 +2,7 @@
  "cells": [
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [
     {
@@ -20,73 +20,46 @@
     }
    ],
    "source": [
-    "def merge(arr, l, m, r): \n",
-    "    n1 = m - l + 1\n",
-    "    n2 = r- m \n",
+    "def partition(arr,low,high): \n",
+    "    i = ( low-1 )         \n",
+    "    pivot = arr[high]\n",
     "  \n",
-    "    # create temp arrays \n",
-    "    L = [0] * (n1) \n",
-    "    R = [0] * (n2) \n",
+    "    for j in range(low , high): \n",
     "  \n",
-    "    # Copy data to temp arrays L[] and R[] \n",
-    "    for i in range(0 , n1): \n",
-    "        L[i] = arr[l + i] \n",
+    "        # If current element is smaller than or \n",
+    "        # equal to pivot \n",
+    "        if   arr[j] <= pivot: \n",
+    "          \n",
+    "            # increment index of smaller element \n",
+    "            i = i+1 \n",
+    "            arr[i],arr[j] = arr[j],arr[i] \n",
     "  \n",
-    "    for j in range(0 , n2): \n",
-    "        R[j] = arr[m + 1 + j] \n",
+    "    arr[i+1],arr[high] = arr[high],arr[i+1] \n",
+    "    return ( i+1 ) \n",
     "  \n",
-    "    # Merge the temp arrays back into arr[l..r] \n",
-    "    i = 0     # Initial index of first subarray \n",
-    "    j = 0     # Initial index of second subarray \n",
-    "    k = l     # Initial index of merged subarray \n",
+    "# The main function that implements QuickSort \n",
+    "# arr[] --> Array to be sorted, \n",
+    "# low  --> Starting index, \n",
+    "# high  --> Ending index \n",
     "  \n",
-    "    while i < n1 and j < n2 : \n",
-    "        if L[i] <= R[j]: \n",
-    "            arr[k] = L[i] \n",
-    "            i += 1\n",
-    "        else: \n",
-    "            arr[k] = R[j] \n",
-    "            j += 1\n",
-    "        k += 1\n",
+    "# Function to do Quick sort \n",
+    "def quickSort(arr,low,high): \n",
+    "    if low < high: \n",
     "  \n",
-    "    # Copy the remaining elements of L[], if there \n",
-    "    # are any \n",
-    "    while i < n1: \n",
-    "        arr[k] = L[i] \n",
-    "        i += 1\n",
-    "        k += 1\n",
-    "  \n",
-    "    # Copy the remaining elements of R[], if there \n",
-    "    # are any \n",
-    "    while j < n2: \n",
-    "        arr[k] = R[j] \n",
-    "        j += 1\n",
-    "        k += 1\n",
-    "  \n",
-    "# l is for left index and r is right index of the \n",
-    "# sub-array of arr to be sorted \n",
-    "def mergeSort(arr,l,r): \n",
-    "    if l < r: \n",
-    "  \n",
-    "        # Same as (l+r)/2, but avoids overflow for \n",
-    "        # large l and h \n",
-    "        m = (l+(r-1))/2\n",
-    "  \n",
-    "        # Sort first and second halves \n",
-    "        mergeSort(arr, l, m) \n",
-    "        mergeSort(arr, m+1, r) \n",
-    "        merge(arr, l, m, r) \n",
+    "        # pi is partitioning index, arr[p] is now \n",
+    "        # at right place \n",
+    "        pi = partition(arr,low,high) \n",
     "  \n",
+    "        # Separately sort elements before \n",
+    "        # partition and after partition \n",
+    "        quickSort(arr, low, pi-1) \n",
+    "        quickSort(arr, pi+1, high) \n",
     "  \n",
     "# Driver code to test above \n",
-    "arr = [12, 11, 13, 5, 6, 7] \n",
+    "arr = [10, 7, 8, 9, 1, 5] \n",
     "n = len(arr) \n",
-    "print (\"Given array is\") \n",
-    "for i in range(n): \n",
-    "    print (\"%d\" %arr[i]), \n",
-    "  \n",
-    "mergeSort(arr,0,n-1) \n",
-    "print (\"\\n\\nSorted array is\") \n",
+    "quickSort(arr,0,n-1) \n",
+    "print (\"Sorted array is:\") \n",
     "for i in range(n): \n",
     "    print (\"%d\" %arr[i]), "
    ]