leetcode 383. 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

简单map

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