solutions for Exercises 1-5

Exercise_1.py

@@ -5,7 +5,15 @@
 # if present, else returns -1 
 def binarySearch(arr, l, r, x): 
 
-  #write your code here
+  while l <= r:
+    m = l + (r - l) // 2
+    if arr[m] == x:
+      return m
+    if arr[m] < x:
+      l = m + 1
+    else:
+      r = m - 1
+  return -1
 
 
 
@@ -17,6 +25,6 @@ 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 % d" % result) 
 else: 
-    print "Element is not present in array"
+  print("Element is not present in array")

Exercise_2.py

@@ -4,20 +4,30 @@
 def partition(arr,low,high):
 
 
-    #write your code here
+    pivot = arr[high]
+    i = low - 1
+    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
 
 
 # Function to do Quick sort 
 def quickSort(arr,low,high): 
 
-    #write your code here
+    if low < high:
+        pi = partition(arr, low, high)
+        quickSort(arr, low, pi - 1)
+        quickSort(arr, pi + 1, high)
 
 # Driver code to test above 
 arr = [10, 7, 8, 9, 1, 5] 
 n = len(arr) 
 quickSort(arr,0,n-1) 
-print ("Sorted array is:") 
+print("Sorted array is:") 
 for i in range(n): 
-    print ("%d" %arr[i]), 
+    print("%d" % arr[i])
 
 

Exercise_3.py

@@ -3,18 +3,29 @@ 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): 
+        if self.head is None:
+            return
+        slow = self.head
+        fast = self.head
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+        print(slow.data)
 
 # Driver code 
 list1 = LinkedList() 

Exercise_4.py

@@ -1,12 +1,40 @@
 # Python program for implementation of MergeSort 
 def mergeSort(arr):
 
-  #write your code here
+  if len(arr) > 1:
+    mid = len(arr) // 2
+    L = arr[:mid]
+    R = arr[mid:]
+
+    mergeSort(L)
+    mergeSort(R)
+
+    i = j = k = 0
+    while i < len(L) and j < len(R):
+      if L[i] <= R[j]:
+        arr[k] = L[i]
+        i += 1
+      else:
+        arr[k] = R[j]
+        j += 1
+      k += 1
+
+    while i < len(L):
+      arr[k] = L[i]
+      i += 1
+      k += 1
+
+    while j < len(R):
+      arr[k] = R[j]
+      j += 1
+      k += 1
 
 # Code to print the list 
 def printList(arr): 
 
-    #write your code here
+  for i in range(len(arr)):
+    print(arr[i], end=" ")
+  print()
 
 # driver code to test the above code 
 if __name__ == '__main__': 

Exercise_5.py

@@ -2,9 +2,25 @@
 
 # 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:
+      p = partition(arr, l, h)
+      if p - 1 > l:
+        stack.append((l, p - 1))
+      if p + 1 < h:
+        stack.append((p + 1, h))