Day3. RansomeNote.cpp

/*

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

*/

//solution 1

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

//solution 2

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) {
        std::ios_base::sync_with_stdio(false);
        unordered_map<char,int> mp;
        for(int i=0;i<magazine.size();i++){
            mp[magazine[i]]++;
        }
        
        for(int i=0;i<ransomNote.size();i++){
            char c=ransomNote[i];
            if(mp.find(c)==mp.end()){
                return false;
            }else{
                mp[c]--;
                if(mp[c]==0){
                    mp.erase(c);
                }
            }
        }
        return true;
    }
};