3. Ransom Note.cpp

/*

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

*/

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) 
    {
        multiset<char>s;
        int len=0;
        
        for(auto x:magazine)
            s.insert(x);
        
        for(auto x:ransomNote)
        {
            if(s.count(x))
            {
                s.erase(s.lower_bound(x));
                len++;
            }
        }
        
    return len==ransomNote.size()?true:false;
    }
};


// Algorithm / Data Structure: MultiSet
// TC: O(n)
// SC: O(1)