/*
 * File: tsp.kt
 * Purpose: Tests the naive O(n!) TSP algorithm.
 * Compilation: kotlinc tsp.kt
 * Execution: kotlin TspKt
 * Author: San Skulrattanakulchai
 */

fun tsp(dist: Array<IntArray>) {
    val pi = IntArray(dist.size) { it }
    var minDist = Int.MAX_VALUE

    fun swap(i: Int, j: Int) {
        val tmp = pi[i]
        pi[i] = pi[j]
        pi[j] = tmp
    }

    fun perm(i: Int) {
        val n = dist.size
        if (i == n-1) {
            minDist = kotlin.math.min(minDist, pi.sumBy {
                dist[pi[it]][pi[(it+1) % n]]
            })
        } else for (j in i until n) {
            swap(i, j)
            perm(i+1)
            swap(i, j)
        }
    }

    perm(1)
    println("minimum tour length = $minDist")
}

fun main(args: Array<String>) {
    val dist = arrayOf<IntArray>(
            intArrayOf(0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10),
            intArrayOf(9,  0,  8,  7,  6,  5,  4,  3, 10,  1,  2),
            intArrayOf(8,  7,  0,  6,  5,  4,  3,  2,  9, 10,  1),
            intArrayOf(7,  6,  5,  0,  4,  3,  2,  1,  8,  9, 10),
            intArrayOf(4,  3,  2,  1,  0, 10,  9,  8,  7,  6,  5),
            intArrayOf(10,  9,  8,  7,  6,  0,  5,  4,  3,  2,  1),
            intArrayOf(7,  8,  9, 10,  1,  2,  0,  3,  4,  5,  6),
            intArrayOf(5,  4,  3,  2,  1,  6,  7,  0,  8,  9, 10),
            intArrayOf(10,  9,  8,  7,  6,  5,  4,  3,  0,  2,  1),
            intArrayOf(1,  2,  4,  3,  6,  5,  8,  7, 10,  0,  9),
            intArrayOf(3,  2,  1,  6,  5,  4,  9,  8,  7, 10,  0)
           )
    tsp(dist)
}