Leetcode Ransom-Note

2022-06-14 13:19

Algorithms:

#algorithm #hash_table

Data structures:

#DS #string #array

Difficulty:

#leetcode #coding_problem #difficulty_easy

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.

Examples

Example 1:

**Input:** s = "leetcode"
**Output:** 0

Example 2:

**Input:** s = "loveleetcode"
**Output:** 2

Example 3:

**Input:** s = "aabb"
**Output:** -1

Constraints

Constraints:

1 <= s.length <= 105
s consists of only lowercase English letters.

Thoughts

Super simple hash map, similar to Leetcode First-Unique-Character-In-a-String

Solution

O(m + n)

class Solution {
public:
  bool canConstruct(string ransomNote, string magazine) {
    // hashmap, O(m + n)
    int hashMap[26] = {};

    for (char c : magazine) {
      hashMap[c - 'a']++;
    }

    for (char c : ransomNote) {
      if (hashMap[c - 'a']-- == 0)
        return false;
    }
    return true;
  }
};

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