Merge pull request larissalages#17 from shaswatsingh19/master

searching and sorting algorithm

Author: larissalages

classical_algorithms/Binary search.py

@@ -0,0 +1,23 @@
+def binary(arr,low,high,x):
+    while low < high:
+        mid = low + (high-1) // 2
+        if(arr[mid] == x):
+            return mid
+        elif(arr[mid] <x):
+            low = mid + 1
+        else:
+            high = mid - 1
+    return -1
+
+n =int(input("Enter a sorted list of number\n"))
+arr =[]
+for i in range(n):
+    arr.append(int(input()))
+
+x =int(input("ENter the number to find\n"))
+
+result = binary(arr,0,len(arr)-1,x)
+if(result == -1):
+    print("Element not found")
+else:
+    print("Element found at ",result+1," position")

classical_algorithms/Heap Sort.py

@@ -0,0 +1,40 @@
+def heapify(arr, n, i): 
+	largest = i # Initialize largest as root 
+	l = 2 * i + 1	 # left = 2*i + 1 
+	r = 2 * i + 2	 # right = 2*i + 2 
+
+	# See if left child of root exists and is 
+	# greater than root 
+	if l < n and arr[i] < arr[l]: 
+		largest = l 
+
+	# See if right child of root exists and is 
+	# greater than root 
+	if r < n and arr[largest] < arr[r]: 
+		largest = r 
+
+	# Change root, if needed 
+	if largest != i: 
+		arr[i],arr[largest] = arr[largest],arr[i] # swap 
+
+		# Heapify the root. 
+		heapify(arr, n, largest) 
+
+def heapSort(arr): 
+	n = len(arr) 
+
+	# Build a maxheap. 
+	for i in range(n//2 - 1, -1, -1): 
+		heapify(arr, n, i) 
+
+	# One by one extract elements 
+	for i in range(n-1, 0, -1): 
+		arr[i], arr[0] = arr[0], arr[i] # swap 
+		heapify(arr, i, 0) 
+
+print('Enter a list of numbers')
+arr = list(map(int,input().split()))
+heapSort(arr) 
+print('After performing heap sort')
+for i in arr:
+    print(i,end =' ')

classical_algorithms/Linear Search .py

@@ -0,0 +1,31 @@
+def linear(arr,n,x):
+    for i in range(n):
+        if(arr[i] == x):
+            return i
+    return -1
+
+n = int(input("Enter the total number of elements\n"))
+arr =list(map(int,input().split()))
+x = int(input("Enter which element you want to find\n"))
+result = linear(arr,n,x)
+if (result == -1):
+        print("Element not found")
+else:
+        print("Element found at" ,result+1,"position")
+
+        
+
+
+    
+
+
+    
+
+
+
+    
+
+    
+
+
+    

classical_algorithms/Sieve of Eratosthenes.py

@@ -0,0 +1,28 @@
+import math
+# taking input
+n  = int(input())
+# making a list named primes
+    # initialize primes with 1 only 
+# here 1 represent the value is prime 
+primes = [1]*(n+1)
+
+# making first and second values as 0
+# as  0, 1 is not a prime and start by checking 
+# from second value
+primes[0] = 0
+primes[1] = 0
+
+# looping through 2,sqrt(n)+1 as every number 
+# comes with 2 factor if first factor is seen then
+# we don't have to look for second one
+# in second loop we are initialize all multiple of 
+# i in first loop
+for i in range(2,int(math.sqrt(n)+1)):
+    if primes[i] ==1:
+    	for  j in range(i*i,n+1,i):
+	    	primes[j] = 0
+
+# printing all primes
+for i in range(len(primes)):
+    if primes[i] == 1:
+        print(i,end = " ")

classical_algorithms/selection sort.py

@@ -0,0 +1,15 @@
+n = int(input())
+li = []
+for i in range(n):
+    m = int(input())
+    li.append(m)
+
+for i in range(n):
+    mini = i 
+    for j in range(i+1,n):
+        if(li[j] < li[mini]):
+            mini = j
+    temp = li[i]
+    li[i] = li[mini]
+    li[mini] = temp
+    print(li)