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") -> falsecanConstruct("aa", "ab") -> falsecanConstruct("aa", "aab") -> true

class Solution {public:    bool canConstruct(string ransomNote, string magazine) {        unordered_map
     
       hashMap;        for(char ch : magazine){            ++hashMap[ch];        }                for(char ch :ransomNote){            if(--hashMap[ch]<0)                return false;        }                return true;    }};