LeetCode in Kotlin

2654. Minimum Number of Operations to Make All Array Elements Equal to 1

Medium

You are given a 0-indexed array nums consisiting of positive integers. You can do the following operation on the array any number of times:

• Select an index i such that 0 <= i < n - 1 and replace either of nums[i] or nums[i+1] with their gcd value.

Return the minimum number of operations to make all elements of nums equal to 1. If it is impossible, return -1.

The gcd of two integers is the greatest common divisor of the two integers.

Example 1:

Input: nums = [2,6,3,4]

Output: 4

Explanation: We can do the following operations:

• Choose index i = 2 and replace nums[2] with gcd(3,4) = 1. Now we have nums = [2,6,1,4].
• Choose index i = 1 and replace nums[1] with gcd(6,1) = 1. Now we have nums = [2,1,1,4].
• Choose index i = 0 and replace nums[0] with gcd(2,1) = 1. Now we have nums = [1,1,1,4].
• Choose index i = 2 and replace nums[3] with gcd(1,4) = 1. Now we have nums = [1,1,1,1].

Example 2:

Input: nums = [2,10,6,14]

Output: -1

Explanation: It can be shown that it is impossible to make all the elements equal to 1.

Constraints:

• 2 <= nums.length <= 50
• 1 <= nums[i] <= 106

Follow-up:

The O(n) time complexity solution works, but could you find an O(1) constant time complexity solution?

Solution

class Solution {
    fun minOperations(nums: IntArray): Int {
        var g = nums[0]
        var list = mutableListOf<Int>()
        var padding = 0
        var result = nums.size
        for (i in 0 until nums.size) {
            val n = nums[i]
            if (n == 1) {
                result--
            }
            g = gcd(g, n)
            if (i == nums.size - 1) continue
            val m = nums[i + 1]
            list.add(gcd(m, n))
        }
        if (g > 1) return -1
        while (!list.any { it == 1 }) {
            padding++
            val nlist = mutableListOf<Int>()
            for (i in 0 until list.size - 1) {
                val n = list[i]
                val m = list[i + 1]
                nlist.add(gcd(m, n))
            }
            list = nlist
        }
        return result + padding
    }

    private fun gcd(a: Int, b: Int): Int = if (b != 0) gcd(b, a % b) else a
}

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