PAT 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

思路:
    1.n1 始终和 n3相同
    2.n2 >= n1 , n2 >= n3
    3.n1 和 n3 要尽可能的大,那么也就是最大和n2相同了,此时 n1 + n2 + n3 - 2 == len(str),因此 n1 = n2 = n3 = (len + 2) / 3

#include<iostream>
using namespace std;
int main(){

    string str;
    
    cin>>str;

    int len = str.size();

    int side = (len + 2) / 3;

    int low = len - side * 2;

    int st = 0,ed = str.size() - 1;
    for (int i = 0 ;i < side - 1; ++i){
        cout<<str[st];
        for (int j = 0;j < low; ++j){
            cout<<' ';        
        }
        cout<<str[ed]<<endl;
        st++;
        ed--;
    }
    for (int i = st; i <= ed; ++i)
        cout<<str[i];

    return 0;
}