LeetCode（383）Ransom Note

题目

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

分析

判断能否由字符串magazine中的字符构造出ransom单词。

代码

#include <iostream>
#include <cstdlib>
#include <string>
#include <vector>

using namespace std;

class Solution {
public:
bool canConstruct(string ransomNote, string magazine) {
int rL = ransomNote.length(), mL = magazine.length();

vector<int> v(256, 0);
for (int i = 0; i < mL; ++i)
{
++v[magazine[i]];
}//for

for (int i = 0; i < rL; ++i)
{
--v[ransomNote[i]];

if (v[ransomNote[i]] < 0)
return false;
}//for

return true;
}
};

int main()
{
cout << Solution().canConstruct("a", "b") << endl;

system("pause");

return 0;
}