给定一个数字n，找出1到n(含n)中，经过淘汰后最终剩下到数字。淘汰到规则是：从左到右，删除第一个数字，然后每隔一个数字删除一个，直到到达列表末尾。
重复上面的步骤，但这次是从右到左。也就是，删除最右侧的数字，然后剩下的数字每隔一个删除一个。
不断重复这两步，从左到右和从右到左交替进行，直到只剩下一个数字。
【示例】
输入：9
输出：6
解释：1,2,3,4,5,6,7,8,9中，第一轮淘汰1、3、5、7、9后剩下2、4、6、8，第二轮淘汰4、8剩下2、6，第三轮淘汰2，所以最终结果是6
题目难度：简单
题目来源：CodeWars-Last man standing
def solution(num: int)-> int:
# your code here
assert solution(9) == 6
assert solution(100) == 54
assert solution(1000) == 510
n = 10：
数字集合为：1 2 3 4 5 6 7 8 9 10
第一轮，淘汰左侧，剩下：2 4 6 8 10
第二轮，淘汰右侧，剩下：2 6 10
第三轮，淘汰左侧，剩下：6
不清楚答案为什么是8
8在第二轮就淘汰了啊 
def solution(num: int) -> int:
num = list(range(1, num + 1))
flag = 1
while len(num) != 1:
num = num[flag + 1::2] if len(num) % 2 == 1 and flag == 0 else num[flag::2]
flag = 1 if flag == 0 else 0
return int(num[0])
不是淘汰右侧，是从右到左进行淘汰：
def solution(num:int):
num = [str(i) for i in range(1,num+1)]
x = 1
while len(num) >1:
if x % 2 != 0:
for i in range(len(num)):
if i % 2 == 0:
del num[0]
else:
num.append(num[0])
del num[0]
x+=1
else:
for i in range(len(num)):
if i % 2 == 0:
del num[-1]
else:
num.insert(0,num[-1])
del num[-1]
x+=1
return int(num[0])
def solution (num: int)->int:
test = list(range(1, num + 1, 1))
# print(test)
if len(test) == 1:
return test[0]
else:
test1 = test[1::2]
# print test1
while len(test1) != 1:
test = test1
test1 = test[::-1][1::2]
# print test1
return test1[0]
资产
资产
# daily_20220429
def solution(num: int)-> int:
# your code here
num_list = [str(x+1) for x in range(num)]
round = 1
while len(num_list) > 1:
if round % 2 == 0:
del_num = [e for i, e in enumerate(num_list[::-1]) if i % 2 == 0]
for i in del_num:
num_list.remove(i)
round += 1
else:
del_num = [e for i, e in enumerate(num_list) if i % 2 == 0]
for i in del_num:
num_list.remove(i)
round += 1
return int(num_list[0])
def solution(num: int)-> int:
# your code here
num_list = [i for i in range(1,num+1)]
while len(num_list) > 1:
for item in num_list[::2]:
if len(num_list) == 1:
break
num_list.remove(item)
for item in num_list[::-2]:
if len(num_list) == 1:
break
num_list.remove(item)
return num_list[0]
assert solution(9) == 6
assert solution(100) == 54
assert solution(1000) == 510
优化版本
def solution(num:int) -> int:
num = [i for i in range(1,num+1)]
x = 1
while len(num) >1:
if x % 2 ==0:
num = num[-2::-2]
num.reverse()
x+=1
else:
num = num[1::2]
x+=1
return int(num[0])
def solution(num: int) -> int:
step, res, arrow = 1, 1, 0
while num > 1:
if not num % 2 and arrow % 2:
res -= step
res += step
num >>= 1
step <<= 1
arrow += 1
return res
assert solution(1) == 1
assert solution(9) == 6
assert solution(100) == 54
assert solution(1000) == 510
def solution(num: int)-> int:
# your code here
l = [i for i in range(1, num + 1)]
c = 1
while len(l) > 1:
if c % 2 != 0:
l = [i for i in l if l.index(i) % 2 != 0 ]
else:
l.reverse()
l = [i for i in l if l.index(i) % 2 != 0]
l.reverse()
c += 1
return l[0]
assert solution(1) == 1
assert solution(9) == 6
assert solution(100) == 54
assert solution(1000) == 510
def solution(num: int) -> int:
list_num = [i for i in range(1, num + 1)]
k = 0
begin = 0
end = len(list_num)
step = 2
while True:
list_num_new = [list_num[i] for i in range(begin, end, step)]
for i in list_num_new:
list_num.remove(i)
k = k + 1
if k % 2 == 0:
begin = 0
end = len(list_num)
step = 2
else:
begin = len(list_num) - 1
end = -1
step = -2
if len(list_num) == 1:
return list_num[0]
assert solution(9) == 6
assert solution(100) == 54
assert solution(1000) == 510
def solution(num: int)-> int:
l1 = [i for i in range(1,num+1)]
count = 1
while len(l1) != 1:
if len(l1) %2 != 0:
l1 = l1[1::2]
else:
if count % 2 != 0:
l1 = l1[1::2]
else:
l1 = l1[::2]
count += 1
else:
return l1[0]
def solution(num: int)->int:
list = [i for i in range(1,num+1)]
list_new = []
while len(list) > 1:
for i in range(0,len(list)):
if i%2 !=0:
list_new.append(list[i])
if len(list_new) != 1:
list_new.reverse()
list,list_new = list_new,[]
else:
return list_new[0]
assert solution(9) == 6
assert solution(100) == 54
assert solution(1000) == 510