STL map.find返回不正确的元素

Question

I have the following, which seems to be returning the first ie 0th node in the map. I cant figure out whats wrong with this code.

The map.find always returns the first (0th) element. No matter what the inputs are constructed in the 'insert' call.

I am somewhat new to STL , so any help would be appreciated. Is there something that I am missing here ?

class numbers{
public :
    unsigned int data;
    numbers(unsigned int value)    {
        data=value;
    }
};
bool operator<(numbers a, numbers b){
    return (a.data<b.data)?a.data:b.data;
}

class names{
public:
    string s;
    names(int value)    {
        char arr[10];
        itoa(value, arr, 10);
        s=arr;
    }
    void print(){cout<<s;}
};

void main(){
    map<numbers, names> bigmap;
    for(int i=0;i<1000;i++)
        bigmap.insert(pair<numbers,names>( numbers(i), names(i)));
    cout<<"Inserted!";
    map<numbers, names>::iterator p;
    p=bigmap.find(numbers(10));
    p->second.print();//output is always 0
    getchar();
    //Large Lookup test
}

Is there something that I am missing here ? DI need to preallocate the objects and then supply to the insert operation. I dont think STL maps require them to be preallocated. Thanks, any help on that front would be greatly appreciated.

Answer 1

Your comparison operator is wrong. Your implementation will always return true unless a is 0 and is less than the RHS, or b is 0 and is greater than or equal to the LHS. Just return the result of the comparison.

bool operator<(numbers a, numbers b){
    return (a.data<b.data);
}