C++ 动态取变量

#include <stdio.h>
#include <unordered_map>
#include <iostream>

using namespace std;

int main()
{
    int a1 = 1;
    int a2 = 2;
    int a3 = 3;

    std::unordered_map<int, int*> tools;
    tools[1] = &a1;
    tools[2] = &a2;
    tools[3] = &a3;


    std::cout << "修改前" << endl;
    for(int i = 1; i <= 3; i++){
        printf("%d\n",*(tools[i]));
    }


    std::cout << "修改后" <<endl;
    a2= 44;
    *(tools[3]) = 55;

    printf("%d\n",a1);
    printf("%d\n",a2);
    printf("%d\n",a3);

    for(int i = 1; i <= 3; i++){
        printf("%d\n",*(tools[i]));
    }

    return 0;
}