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  • 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);
     
        }
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  • 原文地址:https://www.cnblogs.com/renyualbert/p/5782452.html
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