383. Ransom Note
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
bool canConstruct(string ransomNote, string magazine) { // time: O(m + n); space: O(1)
if (ransomNote.length() > magazine.length()) return false;
vector<int> count(26, 0);
for (char ch : magazine) ++count[ch - 'a'];
for (char ch : ransomNote) {
if (--count[ch - 'a'] < 0) return false;
}
return true;
}
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