Problem: Given a sequence of numbers, show all possible letter combinations in a telephone keypad.
Recursive solution in Python:
keyboard = {
'1': [],
'2': ['a','b','c'],
'3': ['d','e','f'],
'4': ['g','h','i'],
'5': ['j','k','l'],
'6': ['m','n','o'],
'7': ['p','q','r','s'],
'8': ['t','u','v'],
'9': ['w','x','y','z'],
'0': []
}
def printkeys(numbers, prefix=""):
if len(numbers)==0:
print prefix
return
for letter in keyboard[numbers[0]]:
printkeys(numbers[1:], prefix+letter)
printkeys("234")
Output:
adg adh adi aeg aeh aei afg afh afi bdg bdh bdi beg beh bei bfg bfh bfi cdg cdh cdi ceg ceh cei cfg cfh cfi