Ransom Note

Problem

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

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

Constraints

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

Solution

The problem Ransom Note can be solved using a hash map to count the number of each letters in both strings.

Implementation

class Solution
{
  public:
    bool canConstruct(string ransomNote, string magazine)
    {
        int letters[26];
        for (int i = 0; i < 26; i++)
            letters[i] = 0;

        for (char ch : magazine)
            letters[ch - 'a'] += 1;

        for (char ch : ransomNote)
            if (letters[ch - 'a']-- == 0)
                return false;

        return true;
    }
};