这是一个很简单的unordered_map写成的字典，就是把一个vector里的元素编号然后两两求和：

# include <iostream>
# include <cstdio>
# include <vector>
# include <unordered_map>
using namespace std;
class Sum2
    {
    public:
    vector<int> Sum_2(vector<int> &num, int target)
        {
        unordered_map<int, int> mapping;
        vector<int> Sum2_array;
        for (int i = 0; i < num.size(); i++)
            mapping[num[i]] = i;
        for (int i = 0; i < num.size(); i++)
            {
            const int gap = target - num[i];
            if (mapping.find(gap) != mapping.end() && mapping[gap] > i)
                {
                Sum2_array.push_back(i + 1);
                Sum2_array.push_back(mapping[gap] + 1);
                break;
                }
            }
        return Sum2_array;
        }
    };
int main()
    {
    Sum2 class_s2;
    return 0;
    }

代码应该是对的，但是运行起来报错：
In file included from /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/unordered_map:35,
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/c++0x_warning.h:31:2:

error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options.

我的<unordered_map>是不是没有安装好？还是我的编译器gcc或者g++有问题？

谢谢！

error中说得很明白了呀
另外，你的gcc版本也太低了，最新的是6.3

已经解决了。谢谢！