DisjointSet.kt

/*
 * Copyright (c) 2017 Kotlin Algorithm Club
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package io.uuddlrlrba.ktalgs.datastructures

class DisjointSet(val size: Int) {
    private val parent = IntArray(size)
    private val rank = ByteArray(size)
    public var count = size
        private set

    init {
        for (i in parent.indices) {
            parent[i] = i
        }
    }

    public fun connected(v: Int, w: Int): Boolean {
        return find(v) == find(w)
    }

    public fun find(v: Int): Int {
        var v = v
        while (parent[v] != v) {
            parent[v] = parent[parent[v]]
            v = parent[v]
        }
        return v
    }

    public fun union(v: Int, w: Int) {
        val rootV = find(v)
        val rootW = find(w)
        if (rootV == rootW) return
        if (rank[rootV] > rank[rootW]) {
            parent[rootW] = rootV
        } else if (rank[rootW] > rank[rootV]) {
            parent[rootV] = rootW
        } else {
            parent[rootV] = rootW
            rank[rootW]++
        }
        count--
    }
}