[383]Ransom Note

【題目描述】


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      

【題目了解】

給定兩個字元串，判斷字元串A是否能夠由B中的字元組成。

水題，直接用哈希表解決

【代碼】

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) {
        map<char,int> m;
        for(int i=0;i<magazine.size();i++){
            m[magazine[i]]++;
        }
        for(int i=0;i<ransomNote.size();i++){
            if(m[ransomNote[i]]==0) return false;
            else m[ransomNote[i]]--;
        }
        return true;
    }
};