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.
手写以ch-'a'建立的map可以更快，不过懒得写了。
class Solution {
public boolean canConstruct(String ransomNote, String magazine) {
HashMap<Character,Integer> map = new HashMap<>();
for(int i = 0 ;i<magazine.length();i++)
{
char ch = magazine.charAt(i);
map.put(ch,map.containsKey(ch)?map.get(ch)+1:1);
}
for(int i = 0 ;i<ransomNote.length();i++)
{
char ch = ransomNote.charAt(i);
if(map.containsKey(ch))
{
int count =map.get(ch);
if (count==0)
return false;
else
map.put(ch,count-1);
}
else
return false;
}
return true;
}
}
