[leetcode] 383. Ransom Note 解题报告

题目链接: https://leetcode.com/problems/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

思路: 一个hash表即可

代码如下:

class Solution {
public:
bool canConstruct(string ransomNote, string magazine) {
unordered_map<char, int> hash;
for(auto ch: magazine) hash[ch]++;
for(auto ch: ransomNote)
if(--hash[ch]<0) return false;
return true;
}
};