Ransom Note

Problem statement

Given two strings ransomNote and magazine, return true if ransomNote can be constructed from magazine and false otherwise.

Each letter in magazine can only be used once in ransomNote.

Example 1:

Input: ransomNote = "a", magazine = "b"Output: false

Example 2:

Input: ransomNote = "aa", magazine = "ab"Output: false

Example 3:

Input: ransomNote = "aa", magazine = "aab"Output: true

Constraints:

• 1 <= ransomNote.length, magazine.length <= 105
• ransomNote and magazine consist of lowercase English letters.

My solution

/**
 * @param {string} ransomNote
 * @param {string} magazine
 * @return {boolean}
 */
var canConstruct = function(ransomNote, magazine) {
    const memo = new Map();
    
    for (const char of magazine.split("")) {
        if (!memo.has(char)) {
            memo.set(char, 0)
        }
        memo.set(char, memo.get(char) + 1)
    }
    
    for (const char of ransomNote.split("")) {
        if (!memo.has(char) || memo.get(char) === 0) {
            return false
        }
        
        memo.set(char, memo.get(char) - 1)
    }
    
    return true;
};