Algorithms Problem Solving: Ransom Note
This post is part of the Algorithms Problem Solving series. And it was originally published on TK's blog.
Problem description
This is the Ransom Note problem. The description looks like this:
Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines; otherwise, it will return false.
Each letter in the magazine string can only be used once in your ransom note.
Examples
# ransomNote = "a", magazine = "b"
# => false
# ransomNote = "aa", magazine = "ab"
# => false
# ransomNote = "aa", magazine = "aab"
# => true
Solution
def can_construct(ransom_note, magazine):
if ransom_note == '':
return True
if magazine == '':
return False
letters_counter = {}
for letter in magazine:
if letter in letters_counter:
letters_counter[letter] += 1
else:
letters_counter[letter] = 1
for char in ransom_note:
if char not in letters_counter or letters_counter[char] == 0:
return False
letters_counter[char] -= 1
return True
