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zigzag.py

#! /usr/bin/env python

import sys

def prt(x):
    i = 0
    while i <= x:
        if i*(i+1)/2 >= x:
            break
        i += 1
    k = x-(i-1)*i/2

#   sys.stdout.write("{:4d}: {}, {}\n".format(x, i, k))
#   if i == x-(i-1)*i/2:
#       sys.stdout.write("\n")

    if 0 == i % 2:
        sig = +1
    else:
        sig = -1
    sys.stdout.write("{}{}\n".format(" " * (20 + sig * (k - i / 2)), x))

for i in xrange(50):
    prt(i)