Leetcode 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

Solution:

• hashtable:asdf

 public bool CanConstruct(string ransomNote, string magazine) {
        int magLength = magazine.Length;
        int ranLength = ransomNote.Length;

        if(ranLength>magLength) return false;
        if(ranLength==0) return true;
        Hashtable hashtable = new Hashtable();
        
        for(int j = 0; j< ranLength;j++)
        {
            if(hashtable.ContainsKey(ransomNote[j]))
            {
                int temp = (int)hashtable[ransomNote[j]];
                temp++;
                hashtable[ransomNote[j]] = temp;
            }
            else
            {
                hashtable.Add(ransomNote[j],1);
            }
        }
        
        for(int i= 0; i< magLength;i++)
        {
            if(hashtable.ContainsKey(magazine[i]))
            {
                int temp = (int)hashtable[magazine[i]];
                if(--temp <=0)  hashtable.Remove(magazine[i]);
                else hashtable[magazine[i]] = temp;
            }
            if(hashtable.Count==0) return true;
        }
        
        
        return false;
    }

 

• 2 pointer & sorting

public bool CanConstruct(string ransomNote, string magazine) {
        int magLength = magazine.Length;
        int ranLength = ransomNote.Length;

        if(ranLength>magLength) return false;
        if(ranLength==0) return true;
        
        var charR = ransomNote.ToCharArray();
        var charM = magazine.ToCharArray();
        Array.Sort(charR);
        Array.Sort(charM);
        int i = 0;
        int j = 0;
        while(j<magLength && i< ranLength)
        {
            if(charR[i] == charM[j])
            {
                i++;
                j++;
            }
            else if(charR[i] < charM[j])
            {
               return false;
            }
            else j++;
        }
        return (i== ranLength);
 
    }