C++ 从 std::map 中查找具有最大值的元素
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find element with max value from std::map
提问by aj3423
I'm trying to get the element with max value from std::map,
我试图从 std::map 中获取具有最大值的元素，
int main() {
map<int, int> m;
m[1] = 100;
m[2] = -1;
auto x = std::max_element(m.begin(), m.end(), m.value_comp());
cout << x->first << " : " << x->second << endl;
}
why it prints the second element 2 : -1?
为什么它打印第二个元素2 : -1？
回答by Levi
Taken from here:
取自这里：
auto x = std::max_element(m.begin(), m.end(),
[](const pair<int, int>& p1, const pair<int, int>& p2) {
return p1.second < p2.second; });
This, rather than using std::map::value_comp()(which compares the key values) looks at the secondmember in the pair, which contains the value. This uses a lambda expression, so you will have to compile with C++11 support
这不是使用std::map::value_comp()（比较键值）查看second对中包含值的成员。这使用了 lambda 表达式，因此您必须使用 C++11 支持进行编译
回答by kfsone
http://www.cplusplus.com/reference/map/map/value_comp/
http://www.cplusplus.com/reference/map/map/value_comp/
Returns a comparison object that can be used to compare two elements to get whether
the key of the first one goes before the second.
and 2 > 1. value_compcompares the keyvalues, not the value values. Because that's how C++ rolls.
并且 2 > 1.value_comp比较键值，而不是值。因为这就是 C++ 的运行方式。
