LeetCode 383. Ransom Note

Posted 2020-08-09

?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

 

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题目，如果前面的字符串中的字母后面一个字符中都有，而且个数不小于前面一个字符串则返回true，否则返回false

 

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) {
        map<char, int> map;
        for (auto &e : ransomNote)
        {
            ++map[e];
        }
        for (auto &e : magazine)
        {
            if (map.find(e) != map.end())
            {
                if (--map[e] == 0)
                {
                    map.erase(e);
                }
            }
        }
        return !map.size();
    }
};