383.Ransom Note

Tags: [map]

Link: https://leetcode.com/problems/ransom-note/\#/description

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.

Note:
You may assume that both strings contain only lowercase letters.

canConstruct("a", "b") -> false
canConstruct("aa", "ab") -> false
canConstruct("aa", "aab") -> true

Solution: Map

class Solution(object):
    def canConstruct(self, ransomNote, magazine):
        """
        :type ransomNote: str
        :type magazine: str
        :rtype: bool
        """
        if not ransomNote:
            return True
        if not magazine:
            return not ransomNote

        c_map = {}
        for c in magazine:
            if c in c_map:
                c_map[c] += 1
            else:
                c_map[c] = 1

        for c in ransomNote:
            if c not in c_map or c_map[c] == 0:
                return False

            c_map[c] -= 1

        return True

Note:

• Time complexity = O(max(n, m)), n is the length of ransomNote, m is the length of the magazine.