PAT (Advanced Level) Practise 1031. Hello World for U (20)

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

代码：

#include <cstdio>
#include <cstring>
int main(){
    char s[85];
    gets(s);
    int N=strlen(s);
    int n1=(N+2)/3,n3=n1,n2=N+2-n1-n3;
    for(int i=0;i<n1-1;i++){
        printf("%c",s[i]);
        for(int j=0;j<n2-2;j++) printf(" ");
        printf("%c\n",s[N-i-1]);
    }
    for(int i=0;i<n2;i++) printf("%c",s[n1+i-1]);
    return 0;
}