用非标准键映射.怎么了？

Question

我正在尝试编写std::map密钥有2个值的容器.这是一个例子:

#include <map>
#include <iostream>

using namespace std;

struct Key {
    int i1; 
    int i2; 

    struct Comparator {
        bool operator() (const Key& k1, const Key& k2) {
            if (k1.i1 < k2.i1)
                return true;
            else if (k1.i2 < k2.i2)
                return true;

            return false;
        }   
    };  
};

int main() {
    std::map<Key, int, Key::Comparator> tree;

    for (int i = 0; i < 100; ++i) {
        for (int j = 0; j < 10; ++j) {
            Key key = {i, j}; 

            tree[key] = i * j;
        }   
    }   
    cout << "tree size: " << tree.size() << endl;

    Key key = {45, 3}; 

    std::map<Key, int, Key::Comparator>::iterator it = tree.find(key);
    if (it == tree.end()) {
        cout << "nothing has found" << endl;
        return 1;
    }   

    cout << "value: " << it->second << endl;

    return 0;
}

它说我"没有找到".我哪里弄错了？我该怎么写Comparator才能让它正常工作？谢谢.

Answer 1

考虑到使用比较器,以下两个是true:

Key(1,2) < Key(2,1)
Key(2,1) < Key(1,2)

您可以使用词典顺序:

return (k1.i1 != k2.i1) ? (k1.i1 < k2.i1)
                        : (k1.i2 < k2.i2);