c++ map 遍历
时间: 2023-10-19 12:35:26 浏览: 50
在C++中,可以使用迭代器、range for循环和C++17的结构化绑定来遍历map。
一种遍历方式是使用迭代器。可以通过使用map的begin()和end()函数来获取map的起始和结束迭代器,然后使用一个循环来迭代访问每个元素。例如,可以使用以下代码进行遍历:
#include <map>
#include <iostream>
int main() {
std::map<int, std::string> mapStudent;
mapStudent = "student_one";
mapStudent = "student_two";
mapStudent = "student_three";
std::map<int, std::string>::iterator iter; // 声明迭代器
for (iter = mapStudent.begin(); iter != mapStudent.end(); iter++) {
std::cout << iter->first << " " << iter->second << std::endl;
}
return 0;
}
另一种遍历方式是使用C++11及以上版本的range for循环。可以直接使用auto关键字来声明一个变量来表示每个键值对,并通过range for循环遍历map。以下是示例代码:
#include <iostream>
#include <unordered_map>
int main() {
std::unordered_map<std::string, int> mp;
mp["张三"] = 20;
mp["李四"] = 18;
mp["王五"] = 30;
std::cout << "方式一、迭代器" << std::endl;
for (auto it = mp.begin(); it != mp.end(); it++) {
std::cout << it->first << " " << it->second << std::endl;
}
std::cout << "\n方法二、range for" << std::endl;
for (auto it : mp) {
std::cout << it.first << " " << it.second << std::endl;
}
std::cout << "\n方法三" << std::endl;
for (auto [key, val] : mp) {
std::cout << key << " " << val << std::endl;
}
return 0;
}
另外还可以使用简单的for循环和size()函数来遍历map。以下是示例代码:
#include <map>
#include <iostream>
int main() {
std::map<int, std::string> mapStudent;
mapStudent = "student_one";
mapStudent = "student_two";
mapStudent = "student_three";
int iSize = mapStudent.size();
for (int i = 1; i <= iSize; i++) {
std::cout << i << " " << mapStudent[i] << std::endl;
}
return 0;
}
以上是C++中遍历map的几种方式。可以根据实际情况选择合适的方式来遍历map。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
#### 引用[.reference_title]
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