/*
* abstract_dsf.c
*
* Copyright (C) 2019, Enric Meinhardt-Llopis, CMLA, ÉNS Paris-Saclay.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

#include <assert.h>

// API
void adsf_assert_consistency(int *t, int n)
{
    assert(n > 0);
    assert(t);
    for (int i = 0; i < n; i++)
    {
        assert(t[i] >= 0);
        assert(t[i] < n);
    }
}

// API
void adsf_begin(int *t, int n)
{
    for (int i = 0; i < n; i++)
        t[i] = i;
}

// API
int adsf_find(int *t, int n, int a)
{
    assert(a >= 0 && a < n);
    if (a != t[a])
        t[a] = adsf_find(t, n, t[a]);
    return t[a];
}

static int adsf_make_link(int *t, int n, int a, int b)
{
    (void)n;
    if (a < b)   // arbitrary choice
    {
        t[b] = a;
        return a;
    }
    else
    {
        t[a] = b;
        return b;
    }
}

// API
int adsf_union(int *t, int n, int a, int b)
{
    assert(a >= 0 && a < n);
    assert(b >= 0 && b < n);
    a = adsf_find(t, n, a);
    b = adsf_find(t, n, b);
    if (a != b)
        b = adsf_make_link(t, n, a, b);
    return b;
}