1 through 5

Exercise_1.py

@@ -5,7 +5,17 @@
 # if present, else returns -1 
 def binarySearch(arr, l, r, x): 
 
-  #write your code here
+    while l <= r: 
+        mid = (l+r)//2
+
+        if arr[mid] == x:
+            return mid 
+        elif arr[mid] > x:
+            r = mid - 1
+        elif arr[mid] < x:
+            l = mid+1
+
+    return -1
 
 
 
@@ -17,6 +27,6 @@ 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

@@ -1,16 +1,53 @@
+# // Time Complexity : Best/Average: O(nlogn), Worst O(n^2) depending on pivot. n^2 if pivot is first or last element
+# // Space Complexity : O(n)
+# // Did this code successfully run on Leetcode :
+# // Any problem you faced while coding this :
+
+
+# // Your code here along with comments explaining your approach
+
+
+
 # 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 is the item that we need to find a position for
+    pivot = arr[low]
+    # 'left' will track the position where elements smaller than pivot go
+    left = low 
+
+    for i in range(low + 1, high + 1): # high + 1 to include the last element
+        if arr[i] < pivot:
+            left += 1
+            # Swap current element with the leftmost available slot
+            arr[i], arr[left] = arr[left], arr[i]
 
-# Function to do Quick sort 
-def quickSort(arr,low,high): 
+    # Finally, move the pivot from the start to its correct sorted position
+    arr[low], arr[left] = arr[left], arr[low]
 
-    #write your code here
+    return left
+
+# PIVOT - THE ITEM I WANT TO FIND A POSITION FOR
+def quickSort(arr, low, high): 
+    if low < high:
+        pivotLocation = partition(arr, low, high) # returns pivot index
+        # Sort elements before and after the pivot
+        quickSort(arr, low, pivotLocation - 1)
+        quickSort(arr, pivotLocation + 1, high)
+
+# [1, 5, 8, 9, 7, 10] 
+#     l        i                
+# quicksort(arr,0,5)
+#   pivotLocation = partition(arr,0,5)
+#                       pivot = arr[0] -> 10
+#                       left = 0
+#                       for i = 1->5
+# pivotLocation = 5
+#   quickSort(arr, 0, 4)
+#       partition(arr,0,4)
+#   quickSort(arr, 6, 5)
+
 
 # Driver code to test above 
 arr = [10, 7, 8, 9, 1, 5] 

Exercise_3.py

@@ -1,20 +1,45 @@
+# // Time Complexity : O(n)
+# // Space Complexity : O(n)
+# // Did this code successfully run on Leetcode :
+# // Any problem you faced while coding this :
+
+
 # Node class  
 class Node:  
 
     # Function to initialise the node object  
-    def __init__(self, data):  
-
+    def __init__(self, data, next=None):  
+        self.data = data 
+        self.next = next 
 class LinkedList: 
 
     def __init__(self): 
-
+        self.head = None
 
     def push(self, new_data): 
-
+        newNode = Node(new_data)
+        if self.head is None:
+            self.head = newNode 
+        else:
+            # 1->2
+            cur = self.head 
+            while cur.next:
+                cur = cur.next 
+
+            cur.next = newNode 
 
+  # 1->2->3->4->5
+  #       t     h 
     # Function to get the middle of  
     # the linked list 
     def printMiddle(self): 
+        tort = self.head 
+        hare = self.head 
+        while hare and hare.next:
+            hare = hare.next.next 
+            tort = tort.next
+
+        return tort 
 
 # Driver code 
 list1 = LinkedList() 

Exercise_4.py

@@ -1,8 +1,42 @@
 # Python program for implementation of MergeSort 
+
+
+# [12, 11, 13, 5, 6, 7]  6
+# left = [12, 11, 13]
+# right= [5, 6, 7]
 def mergeSort(arr):
 
-  #write your code here
-
+    if len(nums) <= 1:
+        return nums 
+
+    mid = len(nums) // 2
+
+    # left = [12, 11, 13]
+    left = mergeSort(nums[:mid])
+    # right= [5, 6, 7]
+    right= mergeSort(nums[mid:])
+
+    return merge(left, right)
+
+# res = [11,12,13]
+# left = [12]
+#           l
+# right =[11,13]
+#             r
+def merge(left,right):
+    res = []
+    l=r=0
+
+    while l < len(left) and r < len(right):
+        if left[l] < right[r]:
+            res.append(left[l])
+            l+=1
+        else:
+            res.append(right[r])
+            r+=1
+
+    res.extend(left[l:])
+    res.extend(right[r:])
 # Code to print the list 
 def printList(arr): 
 

Exercise_5.py

@@ -1,10 +1,40 @@
 # Python program for implementation of Quicksort
 
 # This function is same in both iterative and recursive
-def partition(arr, l, h):
+def partition(arr, low, high):
   #write your code here
+  pivot = arr[low]
+  left = low
+  for i in range(low+1,high+1):
+    if arr[i] < pivot:
+      left+=1
+      arr[i],arr[left] = arr[left], arr[i]
 
+  arr[low],arr[left] = arr[left],arr[low]
+  return left 
 
-def quickSortIterative(arr, l, h):
+
+def quickSortIterative(arr):
   #write your code here
+  size = len(arr)
+  stack = [(0,size-1)]
+
+  while stack:
+    low,high = stack.pop()
+
+    p = partition(arr,low,high)
+
+    if p-1 > low:
+      stack.append((low,p-1))
+
+    if p+1 < high:
+      stack.append((p+1,high))
+
+arr = [10, 7, 8, 9, 1, 5]
+quickSortIterative(arr)
+print("Sorted array:", arr)
+
 
+# stack = [(0,5)]
+# low = 0, high = 5
+# p = partition(arr,0,5)