如何按值对 std::map 进行排序？

例如：

map<string, int> MyMap;
MyMap["3"] = 30;
MyMap["1"] = 10;
MyMap["2"] = 20;
MyMap["4"] = 0;

for (pair<string, int> pair : MyMap) {
    cout << pair.first << ": " << pair.second << '\n';
}
cout << '\n';

map<int, string> reverseMyMap;
for (pair<string, int> pair : MyMap) {
    reverseMyMap[pair.second] = pair.first;
}

cout << "Reverse:\n";
map<int, string>::reverse_iterator it = reverseMyMap.rbegin();
while (it != reverseMyMap.rend()) {
    cout << it->first << ": " << it->second << '\n';
    it++;
}

安慰：

1: 10
2: 20
3: 30
4: 0

Reverse:
30: 3
20: 2
10: 1
0: 4

执行迭代不是从.begin()到.end()，而是从 .rbegin()到.rend()- 简而言之，使用reverse_iterator.

如果求助次数足够多，最好使用boost::multi_index_containerfrom ordered_uniquetostd::string和ordered_non_uniqueto int。