蚂蚁金服开发笔试
1.小红的字符生成（AC）
from math import log
n = int(input())
if n == 1:
print('a')
else:
res = ''
while n:
k = int(log(n, 2))
temp = chr(ord('a')+k)
res += temp
n -= 2**k
print(res) 2.树上节点（妈的，这题不会做，有做过的带老可以教教我）
3.好串数量。（超时了30%）
from collections import Counter, defaultdict strs = input() size = len(strs) res = 0 for i in range(size): for j in range(i, size): acc = Counter(strs[i:j+1]) n1, n2 = 0, 0 for k, v in acc.items(): if v % 2 == 0: n2 += 1 else: n1 += 1 if n1 == 1 and n2>=0: res += 1 print(res)
