使映射键根据插入顺序排序 [英] Make Map Key Sorted According To Insert Sequence

问题描述

没有额外容器(如向量)的帮助，我是否可以使映射的键与插入序列的排序顺序相同?

Without help from additional container (like vector), is it possible that I can make map's key sorted same sequence as insertion sequence?

#include <map>
#include <iostream>

using namespace std;

int main()
{
  map<const char*, int> m;
  m["c"] = 2;
  m["b"] = 2;
  m["a"] = 2;
  m["d"] = 2;


  for (map<const char*, int>::iterator begin = m.begin(); begin != m.end(); begin++) {
      // How can I get the loop sequence same as my insert sequence.
      // c, b, a, d
      std::cout << begin->first << std::endl;
  }

  getchar();
}

推荐答案

没有.std::map 是一个已排序的容器；不维护插入顺序.有许多解决方案使用第二个容器来维护插入顺序 回答另一个相关问题.

No. A std::map is a sorted container; the insertion order is not maintained. There are a number of solutions using a second container to maintain insertion order in response to another, related question.

也就是说，您应该使用 std::string 作为您的密钥.使用 const char* 作为映射键是一个坏主意:它几乎不可能通过键访问或搜索元素，因为只会比较指针，而不是字符串本身.

That said, you should use std::string as your key. Using a const char* as a map key is A Bad Idea: it makes it near impossible to access or search for an element by its key because only the pointers will be compared, not the strings themselves.

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