g2701_2800.s2741_special_permutations.Solution.kt Maven / Gradle / Ivy

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Kotlin-based LeetCode algorithm problem solutions, regularly updated

There is a newer version: 1.30

package g2701_2800.s2741_special_permutations

// #Medium #Array #Dynamic_Programming #Bit_Manipulation #Bitmask
// #2023_08_07_Time_623_ms_(82.35%)_Space_60.8_MB_(52.94%)

class Solution {
    private var dp = HashMap, Long>()
    private var adj = HashMap>()
    private var mod = 1000000007

    private fun count(destIdx: Int, set: Int): Long {
        if (Integer.bitCount(set) == 1) return 1
        val p = destIdx to set
        if (dp.containsKey(p)) {
            return dp[p]!!
        }
        var sum = 0L
        val newSet = set xor (1 shl destIdx)
        for (i in adj[destIdx]!!) {
            if ((set and (1 shl i)) == 0) continue
            sum += count(i, newSet) % mod
            sum %= mod
        }
        dp[p] = sum
        return sum
    }

    fun specialPerm(nums: IntArray): Int {
        for (i in nums.indices) adj[i] = hashSetOf()
        for ((i, vI) in nums.withIndex()) {
            for ((j, vJ) in nums.withIndex()) {
                if (vI != vJ && vI % vJ == 0) {
                    adj[i]!!.add(j)
                    adj[j]!!.add(i)
                }
            }
        }
        if (adj.all { it.value.size == nums.size - 1 }) {
            return (fact(nums.size.toLong()) % mod).toInt()
        }
        var total = 0
        for (i in nums.indices) {
            total += (count(i, (1 shl nums.size) - 1) % mod).toInt()
            total %= mod
        }
        return total
    }

    private fun fact(n: Long): Long {
        if (n == 1L) return n
        return n * fact(n - 1)
    }
}