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  • fewest number of operations needed to get to 1

    package _interview_question
    
    import java.util.*
    
    /**
     * The question is to find the fewest number of operations needed to get to 1.
    available operations:
    - add 1
    - subtract 1
    - divide by 2
    
    Example 1:
    input: 15, output: 5,
    because: 15->16->8->4->2->1
    
    Example 2:
    input: 10, output: 4,
    because: 10->5->4->3->2->1
    
    Have any constraints?
     * */
    class HelpNode(var value: Double) {
        var step: Int = 0
    }
    
    class Solution10 {
        /*
          solution:bfs, Time complexity:O(3^n), Space complexity:O(n)
        * */
        fun getToOne(num: Int): Int {
            val queue = LinkedList<HelpNode>()
            val node = HelpNode(num.toDouble())
            queue.offer(node)
            while (queue.isNotEmpty()) {
                val cur = queue.poll()
                if (cur.value == 1.0) {
                    return cur.step
                }
                val add = cur.value + 1
                val subtract = cur.value - 1
                val divide = cur.value / 2//because divide, so we need double to keep correct
                //println("divide:${divide}")
    
                val addNode = HelpNode(add)
                addNode.step = cur.step + 1
                queue.offer(addNode)
    
                val subtractNode = HelpNode(subtract)
                subtractNode.step = cur.step + 1
                queue.offer(subtractNode)
    
                val divideNode = HelpNode(divide)
                divideNode.step = cur.step + 1
                queue.offer(divideNode)
            }
            return -1
        }
    }
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  • 原文地址:https://www.cnblogs.com/johnnyzhao/p/13311421.html
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