Merge pull request geekcomputers#589 from somnath796/firstbranch

Adding tower of hanoi problem's program and bubble sort algorithm.

Author: geekcomputers

bubble sort.py

@@ -0,0 +1,47 @@
+'''Bubble Sort
+Bubble Sort is the simplest sorting algorithm that works by repeatedly swapping the adjacent elements if they are in wrong order.
+Example:
+First Pass:
+( 5 1 4 2 8 ) –> ( 1 5 4 2 8 ), Here, algorithm compares the first two elements, and swaps since 5 > 1.
+( 1 5 4 2 8 ) –>  ( 1 4 5 2 8 ), Swap since 5 > 4
+( 1 4 5 2 8 ) –>  ( 1 4 2 5 8 ), Swap since 5 > 2
+( 1 4 2 5 8 ) –> ( 1 4 2 5 8 ), Now, since these elements are already in order (8 > 5), algorithm does not swap them.
+
+Second Pass:
+( 1 4 2 5 8 ) –> ( 1 4 2 5 8 )
+( 1 4 2 5 8 ) –> ( 1 2 4 5 8 ), Swap since 4 > 2
+( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
+( 1 2 4 5 8 ) –>  ( 1 2 4 5 8 )
+Now, the array is already sorted, but our algorithm does not know if it is completed. The algorithm needs one whole pass without any swap to know it is sorted.
+
+Third Pass:
+( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
+( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
+( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
+( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )'''
+
+# Python program for implementation of Bubble Sort
+
+def bubbleSort(arr):
+	n = len(arr)
+
+	# Traverse through all array elements
+	for i in range(n):
+
+		# Last i elements are already in place
+		for j in range(0, n-i-1):
+
+			# traverse the array from 0 to n-i-1
+			# Swap if the element found is greater
+			# than the next element
+			if arr[j] > arr[j+1] :
+				arr[j], arr[j+1] = arr[j+1], arr[j]
+
+# Driver code to test above
+arr = [64, 34, 25, 12, 22, 11, 90]
+
+bubbleSort(arr)
+
+print ("Sorted array is:")
+for i in range(len(arr)):
+	print ("%d" %arr[i]),

tower_of_hanoi.py

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+'''Tower of Hanoi is a mathematical puzzle where we have three rods and n disks. The objective of the puzzle is to move
+    the entire stack to another rod, obeying the following simple rules:
+1) Only one disk can be moved at a time.
+2) Each move consists of taking the upper disk from one of the stacks and placing it on top of another stack i.e. a disk
+    can only be moved if it is the uppermost disk on a stack.
+3) No disk may be placed on top of a smaller disk.
+APPROACH:
+Take an example for 2 disks :
+Let rod 1 = 'SOURCE', rod 2 = 'TEMPORARY', rod 3 = 'DESTINATION'.
+
+Step 1 : Shift first disk from 'SOURCE' to 'TEMPORARY'.
+Step 2 : Shift second disk from 'SOURCE' to 'DESTINATION'.
+Step 3 : Shift first disk from 'TEMPORARY' to 'DESTINATION'.
+
+The pattern here is :
+Shift 'n-1' disks from 'SOURCE' to 'TEMPORARY'.
+Shift last disk from 'SOURCE' to 'DESTINATION'.
+Shift 'n-1' disks from 'TEMPORARY' to 'DESTINATION'.
+'''
+def toh(n,s,t,d):
+    if n==1:
+        print(s,'-->',d)
+        return
+    toh(n-1,s,d,t)
+    print(s,'-->',d)
+    toh(n-1,t,s,d)
+
+if __name__=="__main__":
+    while 1:
+
+        n = int(input('''Enter number of disks:'''))
+
+        if n<0:
+            print("Try Again with a valid input")
+            continue
+        elif n==0:
+            break
+        toh(n,'Source','Temporary','Destination')
+
+        print('ENTER 0 TO EXIT')
+