STL贴图合成

Question

#include <iostream>
#include <algorithm>
#include <climits>
#include <map>
#include <unordered_map>
using namespace std;

int main()
{
    std::map<int, std::unordered_map<std::pair<int, int>, int>> region;
    region[0].insert(make_pair(make_pair(1, 1), 1));
    return 0;
}

I am writing the above code and it don't work as expected, How can I fixed it? The error is " error C2064: term does not evaluate to a function taking 1 arguments"

Answer 1

std::pair没有专门的std::hash ，因此它不能用作std::unordered_map的键，除非您提供自定义哈希函数。