From a142692583207a411657902afda4f20d690eabba Mon Sep 17 00:00:00 2001
From: Ranga sai <yalakaranga@gmail.com>
Date: Sat, 18 Jan 2025 19:16:38 -0500
Subject: [PATCH] precourse 1

---
 Exercise_1.py | 15 ++++++++++++---
 Exercise_2.py | 21 +++++++++++++++++----
 Exercise_3.py | 18 +++++++++++++++---
 Exercise_4.py | 33 ++++++++++++++++++++++++++++++---
 Exercise_5.py | 26 ++++++++++++++++++++++----
 5 files changed, 96 insertions(+), 17 deletions(-)

diff --git a/Exercise_1.py b/Exercise_1.py
index 3e6adcf4..4b626253 100644
--- a/Exercise_1.py
+++ b/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")
diff --git a/Exercise_2.py b/Exercise_2.py
index 35abf0dd..cd04cf47 100644
--- a/Exercise_2.py
+++ b/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)
   
  
diff --git a/Exercise_3.py b/Exercise_3.py
index a26a69b8..8a500776 100644
--- a/Exercise_3.py
+++ b/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() 
diff --git a/Exercise_4.py b/Exercise_4.py
index 9bc25d3d..7422a69a 100644
--- a/Exercise_4.py
+++ b/Exercise_4.py
@@ -1,11 +1,38 @@
 # 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 
@@ -13,6 +40,6 @@ def printList(arr):
     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) 
diff --git a/Exercise_5.py b/Exercise_5.py
index 1da24ffb..93cdb22e 100644
--- a/Exercise_5.py
+++ b/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))