5916. 转化数字的最小运算数

Posted 2021-12-03 lgz0921

题目链接：力扣

思路：bfs暴力搜索即可。每一种情况都搜一遍，已经搜过的值标记一下，不要重复搜。越界的值也不需要继续往下搜哦~~~（好久没写bfs了，手生了，忘记标记一开始的start了~~注意一下，一开始的start也要标记一下，要不后面必然也会造成重复搜~~~造成结果错误~~~）

上代码：

class Solution {

    private val numMap = HashMap<Int, Boolean>()
    private val queue = LinkedList<Int>()
    private val dis = Array(1001) { 0 }

    private fun check(x: Int, goal: Int): Boolean {
        if (numMap.containsKey(x) || x != goal && (x < 0 || x > 1000)) {
            return false
        }
        return true
    }

    private fun seek(topValue: Int, value: Int, goal: Int): Int {
        if (check(value, goal)) {
            if (value == goal) {
                return dis[topValue] + 1
            } else {
                dis[value] = dis[topValue] + 1
                queue.add(value)
                numMap[value] = true
            }
        }
        return -2
    }

    fun minimumOperations(nums: IntArray, start: Int, goal: Int): Int {
        queue.add(start)
        dis[start] = 0
        numMap[start] = true
        while (queue.isNotEmpty()) {
            val topValue = queue.poll()
            if (topValue == goal) {
                return dis[topValue]
            }
            for (i in nums.indices) {
                val operationAdd = seek(topValue, topValue + nums[i], goal)
                if (operationAdd != -2) {
                    return operationAdd
                }
                val operationSub = seek(topValue, topValue - nums[i], goal)
                if (operationSub != -2) {
                    return operationSub
                }
                val operationXor = seek(topValue, topValue xor nums[i], goal)
                if (operationXor != -2) {
                    return operationXor
                }
            }
        }
        return -1
    }
}