For some fixed N
, an array A
is beautiful if it is a permutation of the integers 1, 2, ..., N
, such that:
For every i < j
, there is no k
with i < k < j
such that A[k] * 2 = A[i] + A[j]
.
Given N
, return any beautiful array A
. (It is guaranteed that one exists.)
Example 1:
Input: 4 Output: [2,1,4,3]
Example 2:
Input: 5 Output: [3,1,2,5,4]
Note:
1 <= N <= 1000
对于某些固定的
N
,如果数组 A
是整数 1, 2, ..., N
组成的排列,使得:
对于每个 i < j
,都不存在 k
满足 i < k < j
使得 A[k] * 2 = A[i] + A[j]
。
那么数组 A
是漂亮数组。
给定 N
,返回任意漂亮数组 A
(保证存在一个)。
示例 1:
输入:4 输出:[2,1,4,3]
示例 2:
输入:5 输出:[3,1,2,5,4]
提示:
1 <= N <= 1000
16ms
1 class Solution { 2 func beautifulArray(_ N: Int) -> [Int] { 3 var a:[Int] = [Int](repeating: 0,count: N) 4 dfs(1, 0, N, &a,0) 5 for i in 0..<N 6 { 7 a[i] += 1 8 } 9 return a 10 } 11 //深度优先搜索。DFS即Depth First Search. 12 //对每一个可能的分支路径深入到不能再深入为止,而且每个节点只能访问一次 13 func dfs(_ d:Int,_ m:Int,_ n: Int,_ a:inout [Int],_ off:Int) -> Int 14 { 15 var off = off 16 if m >= n {return off} 17 if m + d >= n 18 { 19 a[off] = m 20 off += 1 21 return off 22 } 23 for i in 0..<2 24 { 25 off = dfs(d*2, m+d*i, n, &a, off) 26 } 27 return off 28 } 29 }
原文地址:https://www.cnblogs.com/strengthen/p/9865478.html
时间: 2024-10-08 16:33:47