done with precourse-2

Exercise_1.py

@@ -6,6 +6,20 @@
 def binarySearch(arr, l, r, x): 
 
   #write your code here
+  if len(arr)== 0:
+    return -1
+  middle =  (l+r)//2
+  if x == arr[middle]:
+    return middle
+  else:
+    if x < arr[middle]:
+      return binarySearch(arr,l,(middle-1),x)
+    else:
+      return binarySearch(arr,(middle+1),r,x)
+
+
+
+
 
 
 
@@ -17,6 +31,7 @@ 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

@@ -1,23 +1,31 @@
-# Python program for implementation of Quicksort Sort 
-
-# give you explanation for the approach
-def partition(arr,low,high):
-
-
-    #write your code here
-
+def partition(arr, low, high):
+    pivot = arr[low]  
+    i = low + 1
+    j = high
 
-# Function to do Quick sort 
-def quickSort(arr,low,high): 
-
-    #write your code here
-
-# Driver code to test above 
-arr = [10, 7, 8, 9, 1, 5] 
-n = len(arr) 
-quickSort(arr,0,n-1) 
-print ("Sorted array is:") 
-for i in range(n): 
-    print ("%d" %arr[i]), 
-
-
+    while True:
+        while i <= j and arr[i] <= pivot:
+            i += 1
+        while i <= j and arr[j] > pivot:
+            j -= 1
+        if i > j:
+            break
+        arr[i], arr[j] = arr[j], arr[i]
+    arr[low], arr[j] = arr[j], arr[low]
+    return j
+
+
+def quickSort(arr, low, high):
+    if low < high:
+        mid = partition(arr, low, high)
+        quickSort(arr, low, mid - 1)
+        quickSort(arr, mid + 1, high)
+
+
+if __name__ == "__main__":
+    arr = [10, 7, 8, 9, 1, 5]
+    n = len(arr)
+    print("Original array:", arr)
+    quickSort(arr, 0, n - 1)
+    print("Sorted array is:")
+    print(arr)

Exercise_3.py

@@ -3,18 +3,38 @@ 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): 
-
-
+        node =  Node(new_data)
+        if self.head == None:
+            self.head = node
+        else:
+            curr = self.head
+            while curr.next:
+                curr = curr.next
+            curr.next = node
+
     # Function to get the middle of  
     # the linked list 
     def printMiddle(self): 
+        slow_ptr = self.head
+        fast_ptr = self.head
+        while fast_ptr and fast_ptr.next:
+            slow_ptr = slow_ptr.next
+            fast_ptr =  fast_ptr.next.next
+        if slow_ptr:
+            print(slow_ptr.data)
+        else:
+            print("the linked list is empty")
+
 
 # Driver code 
 list1 = LinkedList() 

Exercise_4.py

@@ -1,18 +1,50 @@
-# Python program for implementation of MergeSort 
 def mergeSort(arr):
-
-  #write your code here
-
-# Code to print the list 
-def printList(arr): 
-
-    #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) 
-    print("Sorted array is: ", end="\n") 
-    printList(arr) 
+    if len(arr) > 1:
+        # Find the middle of the array
+        mid = len(arr) // 2
+
+        # Divide the array into two halves
+        L = arr[:mid]
+        R = arr[mid:]
+
+        # Recursively sort the two halves
+        mergeSort(L)
+        mergeSort(R)
+
+        # Merge the sorted halves
+        i = j = k = 0
+
+        # Copy data to temp arrays L[] and R[]
+        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
+
+        # Check if any element was left
+        while i < len(L):
+            arr[k] = L[i]
+            i += 1
+            k += 1
+
+        while j < len(R):
+            arr[k] = R[j]
+            j += 1
+            k += 1
+
+
+def printList(arr):
+    for i in arr:
+        print(i, end=" ")
+    print()
+
+if __name__ == '__main__':
+    arr = [12, 11, 13, 5, 6, 7]
+    print("Given array is:")
+    printList(arr)
+    mergeSort(arr)
+    print("Sorted array is:")
+    printList(arr)