3n + 1

PoTD_1.py

import sys
values = {1:0}

def cycle(i, j):
    large = 0
    for k in range(min(i,j), max(i,j)+1):
        a = compute(k)
        if (a > large):
            large = a
    print(i, j, large+1)  #(large + 1) because I wasn't including 1 in the length of the cycle.


def compute(k):
    length = 0
    temp = {}
    temp[k] = length
    while (not(values.__contains__(k))):
        if (k%2 == 0):
            k /= 2
        else:
            k = k*3 + 1
        length += 1
        temp[k] = length
    for i in temp.keys():
        values[i] = values[k] + length - temp[i]
    return length + values[k]

def driver():
    for line in sys.stdin.readlines():
        i = line.split()[0]
        j = line.split()[1]
        cycle(i, j)

#too slow to do everycase. PyPy would probably be fast enough
#1 - 700,000 is limit in 3 sec
#1 - 1,000,000 takes a little bit over 4 sec.