LeetCode in Kotlin

433. Minimum Genetic Mutation

Medium

A gene string can be represented by an 8-character long string, with choices from 'A', 'C', 'G', and 'T'.

Suppose we need to investigate a mutation from a gene string startGene to a gene string endGene where one mutation is defined as one single character changed in the gene string.

• For example, "AACCGGTT" --> "AACCGGTA" is one mutation.

There is also a gene bank bank that records all the valid gene mutations. A gene must be in bank to make it a valid gene string.

Given the two gene strings startGene and endGene and the gene bank bank, return the minimum number of mutations needed to mutate from startGene to endGene. If there is no such a mutation, return -1.

Note that the starting point is assumed to be valid, so it might not be included in the bank.

Example 1:

Input: startGene = “AACCGGTT”, endGene = “AACCGGTA”, bank = [“AACCGGTA”]

Output: 1

Example 2:

Input: startGene = “AACCGGTT”, endGene = “AAACGGTA”, bank = [“AACCGGTA”,”AACCGCTA”,”AAACGGTA”]

Output: 2

Constraints:

• 0 <= bank.length <= 10
• startGene.length == endGene.length == bank[i].length == 8
• startGene, endGene, and bank[i] consist of only the characters ['A', 'C', 'G', 'T'].

Solution

import java.util.LinkedList
import java.util.Queue

class Solution {
    private fun isInBank(set: Set<String>, cur: String): List<String> {
        val res: MutableList<String> = ArrayList()
        for (each in set) {
            var diff = 0
            for (i in 0 until each.length) {
                if (each[i] != cur[i]) {
                    diff++
                    if (diff > 1) {
                        break
                    }
                }
            }
            if (diff == 1) {
                res.add(each)
            }
        }
        return res
    }

    fun minMutation(start: String, end: String, bank: Array<String>): Int {
        val set: MutableSet<String> = HashSet()
        for (s in bank) {
            set.add(s)
        }
        val queue: Queue<String> = LinkedList()
        queue.offer(start)
        var step = 0
        while (queue.isNotEmpty()) {
            var curSize = queue.size
            while (curSize-- > 0) {
                val cur = queue.poll()
                if (cur == end) {
                    return step
                }
                for (next in isInBank(set, cur)) {
                    queue.offer(next)
                    set.remove(next)
                }
            }
            step++
        }
        return -1
    }
}

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