c++ 设置结构，set.find() 函数产生错误“无效的比较器”

Question

I make set of structs. My struct has one array with length 8 inside as pointer. If I insert some structs to the set, it's okay. But when I try to find, error('invalid comparator') occurs. Here is my code.

struct Key {
    int* arr;
};

bool operator<(const Key& a, const Key& b) {
    for (int i = 0; i < 8; i++) {
        if (a.arr[i] == b.arr[i]) {
            continue;
        }
        else {
            return a.arr[i] < b.arr[i];
        }
    }

    return true;
}

bool operator==(const Key& a, const Key& b) {
    for (int i = 0; i < 8; i++) {
        if (a.arr[i] != b.arr[i]) {
            return false;
        }
    }

    return true;
}


    set<Key> visit;
    visit.insert(initKey);

......

                Key key;
                key.arr = newcandidate;

                visit.find(key); -> trigger error.

I want to add arrays to somewhere. Then I want to find some arrays in there fastly. So I try to use 'set' structures. What do I need to do to solve this problem? Thank you very much for your reading.

Answer 1

You need to define properly only operator<. The operator== is not relevant to the set. You should return false at last row. The relation is strict. It shouldn't be possible to have a < b and b < a, but your operator is defined to be a < a.