input-comb-loop.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Author: Ray Chen <oldsharp@gmail.com>
# License: Public domain


import sys


TABLE = [
    '0',        # 0
    '1',        # 1
    "abc",      # 2
    "def",      # 3
    "ghi",      # 4
    "jkl",      # 5
    "mno",      # 6
    "pqrs",     # 7
    "tuv",      # 8
    "wxyz"      # 9
]


def f(user_input):
    """Main routine."""
    # This gives a initial pos array: [0, 0, 0, ..., 0].
    pos_array = [0] * len(user_input)

    while True:
        # Get the pos array to be printed this round.
        for i, char in enumerate(user_input):
            if pos_array[i] == len(TABLE[int(char)]):
                if i + 1 == len(user_input):
                    # Finished
                    return
                else:
                    pos_array[i+1] += 1
                pos_array[i] = 0

        # Print the str this round.
        for i, char in enumerate(user_input):
            sys.stdout.write(TABLE[int(char)][pos_array[i]])

        sys.stdout.write('\n')
        pos_array[0] += 1


if __name__ == "__main__":
    while True:
        try:
            f(raw_input("--> "))
        except EOFError:
            print "Bye"
            break

input-comb-tailrecursion.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Author: Ray Chen <oldsharp@gmail.com>
# License: Public domain


import sys


TABLE = [
    '0',        # 0
    '1',        # 1
    "abc",      # 2
    "def",      # 3
    "ghi",      # 4
    "jkl",      # 5
    "mno",      # 6
    "pqrs",     # 7
    "tuv",      # 8
    "wxyz"      # 9
]


def echo(pos_array, user_input):
    """Write chars to stdout according current pos state."""
    for i, char in enumerate(user_input):
        sys.stdout.write(TABLE[int(char)][pos_array[i]])
    sys.stdout.write('\n')


def dfs(pos_array, user_input):
    """Do the tail recursion."""
    # First we print this round's string out.
    echo(pos_array, user_input)

    # Now update the state.
    pos_array[0] += 1
    for i, char in enumerate(user_input):
        if pos_array[i] == len(TABLE[int(char)]):
            if i + 1 == len(user_input):
                # Finished.
                return
            else:
                pos_array[i] = 0
                pos_array[i+1] += 1

    # Do the recursive iteration.
    dfs(pos_array, user_input)


if __name__ == "__main__":
    while True:
        try:
            user_input = raw_input("--> ")
            dfs([0]*len(user_input), user_input)
        except EOFError:
            print "Bye"
            break