C++ map按key排序方法详解

#include <map>
#include <iostream>

int main() {
    std::map<int, std::string> myMap;
    myMap[3] = "three";
    myMap[1] = "one";
    myMap[4] = "four";
    myMap[2] = "two";

    for (const auto& pair : myMap) {
        std::cout << pair.first << ": " << pair.second << "\n";
    }
    return 0;
}

std::map<int, std::string, std::greater<int>> descendingMap;
descendingMap[3] = "three";
descendingMap[1] = "one";
descendingMap[4] = "four";
descendingMap[2] = "two";

for (const auto& pair : descendingMap) {
    std::cout << pair.first << ": " << pair.second << "\n";
}

#include <unordered_map>
#include <vector>
#include <algorithm>

std::unordered_map<int, std::string> unsortedMap = {{3,"three"},{1,"one"},{4,"four"},{2,"two"}};
std::vector<std::pair<int, std::string>> vec(unsortedMap.begin(), unsortedMap.end());

std::sort(vec.begin(), vec.end());
for (const auto& pair : vec) {
    std::cout << pair.first << ": " << pair.second << "\n";
}