383. Ransom Note

📋 Đề Bài

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.

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.

🧠 Thuật Toán & Kỹ Thuật

String (Chuỗi)

⏱️ Thời gian O(n²)

💾 Không gian O(1)

💻 Lời Giải

C++ 0383-ransom-note.cpp

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) {
        int cnt[26] = {0};
        for (char c : magazine) {
            cnt[c - 'a']++;
        }
        for (char c : ransomNote) {
            if (cnt[c - 'a']-- <= 0) {
                return false;
            }
        }
        return true;
    }
};