标签:Beautiful tmp used dic set nouse 932 Array copy
Leetcode:932. Beautiful Array
- 本题难度: Hard
Topic: divide-and-conquer
Description
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
我的代码
import copy
import collections
class Solution:
def beautifulArray(self,N):
memo = {1: [1]}
def f(N):
if N not in memo:
odds = f((N+1)//2)
evens = f(N//2)
memo[N] = [2*x-1 for x in odds] + [2*x for x in evens]
return memo[N]
return f(N)
超时的代码
noUse = {i+1 for i in range(N)}
use = collections.OrderedDict()
stack = [[use,noUse]]
while(len(stack)>0):
[used_dic, nouse_set] = stack.pop()
if len(nouse_set) == 0:
return [item for item in used_dic]
for toUse in nouse_set:
f = 0
for used in used_dic:
tmp = used_dic.get((used+toUse)//2,-1)
if tmp>used_dic[used]:
f = 1
break
if toUse*2-used in nouse_set:
f = 1
break
if f == 1:
continue
tmp_set = copy.copy(nouse_set)
tmp_set.remove(toUse)
tmp_dic = copy.copy(used_dic)
tmp_dic[toUse] = len(used_dic)-1
stack.append([tmp_dic,tmp_set])
思路
分治的思想,对左右半边来说,第一个数只取左边,第二个数只取右边,如果左右两边,一边奇数,一边偶数,则其平均数不会出现。
标签:Beautiful,tmp,used,dic,set,nouse,932,Array,copy 来源: https://www.cnblogs.com/siriusli/p/11255029.html
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