Question

a = int(raw_input("Enter a number to check if it is happy:"))
l = map(int, str(a))
c = 0
while 1:
    for i in l:
       b = i
       c = c + b **2
    if c == 1:
        print "Happy Number!"
        raw_input("Hit enter to end")
        break
    elif c == a:
        print ("Not a Happy number")
        raw_input("Hit enter to end")
        break
    else:
        l = map(int, str(c))

This is the code I have written in Python, it works with the numbers 1 and 0, however any other number I have tried leaves it looping infinitely. Could somebody take a look and see what I have done wrong and suggest a solution? Thanks 🙂

For reference: http://en.wikipedia.org/wiki/Happy_number

Answer 1

Try this:

a = int(raw_input("Enter a number to check if it is happy: "))
visited = set()
while 1:
    if a == 1:
        print "Number is happy!"
        break
    a = sum(int(c) ** 2 for c in str(a))
    if a in visited:
        print "Number is sad!"
        break
    visited.add(a)