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

解法一：使用数组 （14ms）

public class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        //user array,runtime:14ms
        int[] times = new int[26];
        for(char c:magazine.toCharArray()){
        	times[c-'a']++;
        }
        for(char c:ransomNote.toCharArray()){
        	if(--times[c-'a']<0)
        		return false;
        }
        return true;
}
}

解法二：使用hashtable （71ms）

import java.util.Hashtable;
public class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        use Hashtable,runtime:71ms
        Map<Character,Integer> table = new Hashtable<Character, Integer>();
        for(char c:magazine.toCharArray()){
        	if(table.get(c)==null)
        		table.put(c, 1);
        	else
        		table.put(c, table.get(c)+1);
        }
        for(char c:ransomNote.toCharArray()){
        	if(table.get(c)==null||table.get(c)==0)
        		return false;
        	else
        		table.put(c, table.get(c)-1);
        }
        return true; 
    }
}