precourse 2

Exercise_1.py

@@ -4,7 +4,16 @@
 # It returns location of x in given array arr  
 # if present, else returns -1 
 def binarySearch(arr, l, r, x): 
-
+  while l<r:
+    mid = (l+r)//2
+    if arr[mid]==x:
+      return mid
+    else:
+      if arr[mid]>x:
+        r = mid-1
+      elif arr[mid]<x:
+        l = mid+1
+  return -1
   #write your code here
 
 
@@ -17,6 +26,6 @@ def binarySearch(arr, l, r, x):
 result = binarySearch(arr, 0, len(arr)-1, x) 
 
 if result != -1: 
-    print "Element is present at index % d" % result 
+    print("Element is present at index",result)
 else: 
-    print "Element is not present in array"
+    print("Element is not present in array")

Exercise_2.py

@@ -2,13 +2,27 @@
 
 # give you explanation for the approach
 def partition(arr,low,high):
-
-
+
+    i=low-1
+    pivot  = arr[high]
+    for j in range(low,high):
+        if arr[j]<=pivot:
+            i+=1
+            arr[i],arr[j] = arr[j],arr[i]
+
+    arr[i+1],arr[high] = arr[high],arr[i+1]
+
+    return i+1
     #write your code here
 
 
 # Function to do Quick sort 
 def quickSort(arr,low,high): 
+    if low<high:
+        pivot = partition(arr,low,high)
+
+        quickSort(arr, low, pivot-1)
+        quickSort(arr, pivot+1, high)
 
     #write your code here
 
@@ -17,7 +31,6 @@ def quickSort(arr,low,high):
 n = len(arr) 
 quickSort(arr,0,n-1) 
 print ("Sorted array is:") 
-for i in range(n): 
-    print ("%d" %arr[i]), 
+print(arr)
 
 

Exercise_3.py

@@ -3,18 +3,30 @@ class Node:
 
     # Function to initialise the node object  
     def __init__(self, data):  
-
+        self.data= data
+        self.next = None
 class LinkedList: 
 
     def __init__(self): 
-
+        self.head = None
 
     def push(self, new_data): 
-
+        new_node = Node(new_data)
+        new_node.next = self.head
+        self.head = new_node
 
     # Function to get the middle of  
     # the linked list 
     def printMiddle(self): 
+        ptr1 = self.head
+        ptr2 = self.head
+
+        while ptr2 and ptr2.next:
+            ptr1  = ptr1.next
+            ptr2 = ptr2.next.next
+
+        print(ptr1.data)
+        return ptr1
 
 # Driver code 
 list1 = LinkedList() 

Exercise_4.py

@@ -1,18 +1,45 @@
 # Python program for implementation of MergeSort 
 def mergeSort(arr):
+  if len(arr)<=1:
+    return arr
 
+  left =0
+  right = len(arr)
+  mid = (left+right)//2
+
+  left_array=mergeSort(arr[:mid])
+  right_array = mergeSort(arr[mid:])
+
+  i,j=0,0
+  result =[]
+  while i < len(left_array) and j < len(right_array):
+    if left_array[i] < right_array[j]:
+        result.append(left_array[i])
+        i += 1
+    else:
+        result.append(right_array[j])
+        j += 1
+
+  result.extend(left_array[i:])
+  result.extend(right_array[j:])
+
+  return result
+
+
+
   #write your code here
 
 # Code to print the list 
 def printList(arr): 
-
+    print(arr)
+    return
     #write your code here
 
 # driver code to test the above code 
 if __name__ == '__main__': 
     arr = [12, 11, 13, 5, 6, 7]  
     print ("Given array is", end="\n")  
     printList(arr) 
-    mergeSort(arr) 
+    result=mergeSort(arr) 
     print("Sorted array is: ", end="\n") 
-    printList(arr) 
+    printList(result) 

Exercise_5.py

@@ -2,9 +2,27 @@
 
 # This function is same in both iterative and recursive
 def partition(arr, l, h):
-  #write your code here
-
-
+    pivot = arr[h]
+    i = l - 1  
+    for j in range(l, h):
+        if arr[j] <= pivot: 
+            i += 1
+            arr[i], arr[j] = arr[j], arr[i] 
+
+    arr[i + 1], arr[h] = arr[h], arr[i + 1]
+
+    return i + 1 
 def quickSortIterative(arr, l, h):
-  #write your code here
+    stack = []
+    stack.append((l, h))
+
+    while stack:
+        l, h = stack.pop()
+
+        if l < h:
+            pivot_index = partition(arr, l, h)
+
+            stack.append((l, pivot_index - 1))
+
+            stack.append((pivot_index + 1, h))