C++映射 cend()函数用于返回常量迭代器,该常量迭代器位于映射中的最后一个条目旁边。
const_iterator cend() const noexcept; //since C++ 11
它返回一个常量迭代器,指向映射的最后一个元素。
我们来看一个简单的cend()函数示例。
链接:https://www.learnfk.comhttps://www.learnfk.com/c++/cpp-map-cend-function.html
来源:LearnFk无涯教程网
#include <iostream> #include <map> using namespace std; int main () { map<char,int> mymap; mymap['b'] = 100; mymap['a'] = 200; mymap['c'] = 300; //print content: cout << "mymap contains:"; for (auto it = mymap.cbegin(); it != mymap.cend(); ++it) cout << " [" << (*it).first << ':' << (*it).second << ']'; cout << '\n'; return 0; }
输出:
mymap contains: [a:200] [b:100] [c:300]
在上面的示例中,cend()函数用于返回指向mymap映射中最后一个元素旁边的迭代器。
让我们看一个简单的示例,使用for-each循环遍历映射。
#include <iostream> #include <map> #include <string> #include <iterator> #include <algorithm> using namespace std; int main() { map<string, int> m; m["Room1"] = 100; m["Room2"] = 200; m["Room3"] = 300; // Create a map iterator and point to beginning of map map<string, int>::iterator it = m.begin(); // Iterate over a map using std::for_each and Lambda function for_each(m.cbegin(), m.cend(), [](pair<string, int> element){ // Accessing KEY from element string word = element.first; // Accessing VALUE from element. int count = element.second; cout<<word<<" = "<<count<<endl; }); return 0; }
输出:
Room1 = 100 Room2 = 200 Room3 = 300
在上面的示例中,我们使用STL算法std ::for-each遍历映射。它将在每个map元素上进行迭代,并调用我们提供的回调。
让我们看一个使用while循环迭代映射的简单示例。
#include <iostream> #include <map> #include <string> int main() { using namespace std; map<int,string> mymap = { { 100, "Nikita"}, { 200, "Deep" }, { 300, "Priya" }, { 400, "Suman" }, { 500, "Aman" }}; map<int, string>::const_iterator it;//declare an iterator it = mymap.cbegin();//assign it to the start of the vector while (it != mymap.cend())//while it hasn't reach the end { cout << it->first << " = " << it->second << "\n"; // print the value of the element it points to ++it;//and iterate to the next element } cout << endl; }
输出:
100 = Nikita 200 = Deep 300 = Priya 400 = Suman 500 = Aman
在上面的示例中,cend()函数用于返回指向mymap映射中最后一个元素旁边的常量迭代器。
让我们看一个简单的例子。
#include <iostream> #include <string> #include <map> using namespace std; int main () { map<int,int> mymap = { { 10, 10}, { 20, 20 }, { 30, 30 } }; cout<<"Elements are:" <<endl; for (auto it = mymap.cbegin(); it != mymap.cend(); ++it) cout << it->first << " + " << it->second << " = " <<it->first + it->second << '\n'; auto ite = mymap.cend(); cout << "end element (point next to the last): "; cout << "{" << ite->first << ", " << ite->second << "}\n"; return 0; }
输出:
Elements are: 10 + 10 = 20 20 + 20 = 40 30 + 30 = 60 end element (point next to the last): {3, 0}
在上面的示例中,cend()函数用于返回指向mymap映射中最后一个元素旁边的常量迭代器。
祝学习愉快!(内容编辑有误?请选中要编辑内容 -> 右键 -> 修改 -> 提交!)