Question

I have a series of Key value pairs. Each Key has 2 values. Values of Keys may coincide.
Initially, I start with Key1, ValueKey1, ValueKey2 are stored in a set (maybe array).

Now for each consecutive Keyi, I check if Valuei and Valuei+1 are in the set. If any one of them is in the set, then join the set.

Else if both KeyValues are present in a set, discard that key.

How can I implement this thing using C++, I have very little idea, so if possible a code snippet or a hint would be really helpful.

Answer 1

Are you using or in possession of ‘Algorithms in C++‘ (Sedgewick, 3rd ed.) by any chance?

The first problem that is encountered in the book is that of connectivity (page 7) , and in it there are multiple implementations of a union-find (quick-union, quick-find, weighted etc) algorithm that uses paired keys.

Here’s the quick-find version: (This is just a re-type from the book – not tested)

#include <iostream>
const int N = 10000;
int main() {
    int i, p, q, id[N];
    for( i = 0; i < N; i++ ) id[i] = i;
    while( cin >> p >> q ) {
        int t = id[p];
        if ( t = id[q] ) continue;
        for ( i = 0; i < N; i++ )
            if ( id[i] == t) id[i] = id[q];
        cout << " " << p << " " << q << endl;
    }
}

Just keeps spitting out pairs that aren’t connected (which you could probably invert to get what you want)

The book has a pretty detailed description of how it works – and I’m guessing that you have it for now.