PAT 1031 Hello World for U python解法

1031 Hello World for U （20 分）
Given any string of N (≥5) characters, you are asked to form the characters into the shape of U. For example, helloworld can be printed as:

h  d
e  l
l  r
lowo

That is, the characters must be printed in the original order, starting top-down from the left vertical line with n_​1​​ characters, then left to right along the bottom line with n​_​2​​ characters, and finally bottom-up along the vertical line with n​_​3​​ characters. And more, we would like U to be as squared as possible – that is, it must be satisfied that n_​1​​ = n​_​3 ​​= max { k | k ≤ n_​2​​ for all 3 ≤ n_​2 ​​≤ N} with n​_​1 + n​_​2​​ + n_​3​​ − 2 = N.

Input Specification:
Each input file contains one test case. Each case contains one string with no less than 5 and no more than 80 characters in a line. The string contains no white space.

Output Specification:
For each test case, print the input string in the shape of U as specified in the description.

Sample Input:

helloworld!

Sample Output:

h   !
e   d
l   l
lowor

题意：将一串字符U型输出，满足n_​1​​ = n​_​3 ​​= max { k | k ≤ n_​2​​ for all 3 ≤ n_​2 ​​≤ N} with n​_​1 + n​_​2​​ + n_​3​​ − 2 = N.。这里要理解n_​1、n_​2和n_​3指的是哪些字符。如图：蓝色是n_​1，红色是n_​2，绿色是n_​3。

解题思路：理清题意后就很简单了，首先为了满足题设条件，n_​1​​ = n_​3​​ = (N+2)/3，n_​2​​ = N - 2 - n_​1 - n_​3，得到n_​1、n₂、n_​3之后，先输出n_​1-1行，每一行是字符串的头和尾以及中间加上n₂+2个空格，最后输出中间的字符。

s = input()
n1 = (len(s)+2)//3
n2 = len(s) - 2*n1 -2
for i in range(n1-1):
    print(s[i] + ' '*(n2+2) + s[-i-1])
print(s[n1-1:len(s)-n1+1])