创建一个自己的地图比较器 [英] create an own comparator for map
问题描述
typedef map<string, string> myMap;
当向myMap插入一个新对时,它将使用键来比较它自己的字符串比较器。
我不知道我们是否可以覆盖那个比较器。
例如比较键的长度,而不是字母表。
或者反正再次对地图排序。
感谢您的帮助。
When inserting a new pair to myMap, it will use the key to compare by its own string comparator. I don't know whether we can override that comparator or not? For example comparing key by its length, not by the alphabet. Or anyway to sort the map again. Thanks for helping.
推荐答案
std :: map
最多使用四个模板类型参数,第三个是比较器。例如:
std::map
takes up to four template type arguments, the third one being a comparator. E.g.:
struct cmpByStringLength {
bool operator()(const std::string& a, const std::string& b) const {
return a.length() < b.length();
}
};
// ...
std::map<std::string, std::string, cmpByStringLength> myMap;
Alternatively you could also pass a comparator to map
s constructor.
当比较长度时,您只能在地图中将每个长度的一个字符串作为键。
Note however that when comparing by length you can only have one string of each length in the map as a key.
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