LeetCode383. Ransom Note

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

题目大意：给两个string，判断第一个string能否由第二个string里面所含有的字母组成，第二个string里面的所有字母只能使用一次~

分析：建立一个hash数组，对第二个string遍历并记录每个字符出现的次数，然后遍历第一个string，如果有出现hash里面不存在的字符，那么return false~~~~

class Solution {
public:
bool canConstruct(string ransomNote, string magazine) {
vector<int> hash(256);
for(int i = 0; i < magazine.size(); i++)
hash[magazine[i]]++;
for(int i = 0; i < ransomNote.size(); i++)
if(hash[ransomNote[i]])
hash[ransomNote[i]]--;
else
return false;
return true;
}
};