Create Heapsort.py

Sorting/Heapsort.py

@@ -0,0 +1,101 @@
+
+# return left child of `A[i]`
+def LEFT(i):
+    return 2*i + 1
+
+
+# return right child of `A[i]`
+def RIGHT(i):
+    return 2*i + 2
+
+
+#  swap two indices in a list
+def swap(A, i, j):
+
+    temp = A[i]
+    A[i] = A[j]
+    A[j] = temp
+
+
+# Recursive heapify-down algorithm.
+def heapify(A, i, size):
+
+    # get left and right child of node at index `i`
+    left = LEFT(i)
+    right = RIGHT(i)
+
+    largest = i
+
+    # compare `A[i]` with its left and right child
+    # and find the largest value
+    if left < size and A[left] > A[i]:
+        largest = left
+
+    if right < size and A[right] > A[largest]:
+        largest = right
+
+    # swap with a child having greater value and
+    # call heapify-down on the child
+    if largest != i:
+        swap(A, i, largest)
+        heapify(A, largest, size)
+
+
+# Function to remove an element with the highest priority (present at the root)
+def pop(A, size):
+
+    # if the heap has no elements
+    if size <= 0:
+        return -1
+
+    top = A[0]
+
+    # replace the root of the heap with the last element
+    # of the list
+    A[0] = A[size - 1]
+
+    # call heapify-down on the root node
+    heapify(A, 0, size - 1)
+
+    return top
+
+
+# Function to perform heapsort on a list `A` of size `n`
+def heapsort(A):
+
+    # build a priority queue and initialize it by the given list
+    n = len(A)
+
+    # Build-heap: Call heapify starting from the last internal
+    # node all the way up to the root node
+    i = (n - 2) // 2
+    while i >= 0:
+        heapify(A, i, n)
+        i = i - 1
+
+    # repeatedly pop from the heap till it becomes empty
+    while n:
+        A[n - 1] = pop(A, n)
+        n = n - 1
+
+
+if __name__ == '__main__':
+  B=[]
+  n=0
+  print("Please, enter the numbers to be sorted \n Enter 'exit' after entering the numbers")
+
+  while n!="exit":
+    n=input()
+    if n!="exit":
+      B.append(int(n))
+
+  print(f" Unsorted list {B}")
+
+
+
+
+    # perform heapsort on the list
+  heapsort(B)
+
+    # print the sorted list
+  print(f" Sorted list {B}")