#include<iostream>#include<map>intmain(){std::map<int,std::string>myMap;myMap[1]="One";myMap[2]="Two";myMap[3]="Three";int keyToFind=3;if(myMap.contains(keyToFind)){std::cout<<"键 "<<keyToFind<<" 存在于 map 中,值为: "<<myMap[keyToFind]<<std::endl;}else{st...
bool contains( const Key& key ) const; (1) (C++20 起) template< class K > bool contains( const K& x ) const; (2) (C++20 起) 1) 检查容器中是否有关键等价于 key 的元素。 2) 检查是否有键比较等价于值x 的元素。此重载仅若有限定 id Compare::is_transparent 合法且代表类型才参与...
std::map<Key,T,Compare,Allocator>::contains From cppreference.com <cpp |container |map boolcontains(constKey&key)const; (1)(since C++20) template<classK> boolcontains(constK&x)const; (2)(since C++20) 1)Checks if there is an element with key equivalent tokeyin the container. ...
std::cout << "mymap contains:\n"; for (it=mymap.begin(); it!=mymap.end(); ++it) std::cout << it->first << " => " << it->second << '\n'; std::cout << "anothermap contains:\n"; for (it=anothermap.begin(); it!=anothermap.end(); ++it) std::cout << it->fi...
#include <iostream> #include <map> #include <limits> template<typename KeyType, typename ValueType> ValueType mapDefaultInf(const std::map<KeyType, ValueType> & map, const KeyType & key) { if(!map.contains(key)) { return std::numeric_limits<ValueType>::infinity(); } else { return ...
std::mapis a sorted associative container that contains key-value pairs with unique keys. Keys are sorted by using the comparison functionCompare. Search, removal, and insertion operations have logarithmic complexity. Maps are usually implemented asRed–black trees. ...
contains (C++20) 检查容器是否含有带特定键的元素 (公开成员函数) equal_range 返回匹配特定键的元素范围 (公开成员函数) lower_bound 返回指向首个不小于 给定键的元素的迭代器 (公开成员函数) upper_bound 返回指向首个大于 给定键的元素的迭代器 ...
contains (C++20) 检查容器是否含有带特定键的元素 (公开成员函数) count 返回匹配特定键的元素数量 (公开成员函数) upper_bound 返回指向首个大于给定键的元素的迭代器 (公开成员函数) lower_bound 返回指向首个不小于给定键的元素的迭代器 (公开成员函数) equal_range 返回匹配特定键值的元素范围 ...
map<double, double> mymap;mymap[3.0] = 1.0;double t = 0.0;for(int i = 0; i < 31; i++){ t += 0.1; bool contains = (mymap.count(t) > 0);}在上面的示例中,contains将始终为false。我当前的解决方法是乘以t0.1而不是加0.1,如下所示:for(int i = 0; i < 31; i++){ t = ...
std::any 是 c++17 标准新提供的类，作用是存储任意类型的一段内存，并可以重复赋值，在赋值后可以...