PAT 1031 Hello World for U

题目：

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 n1​ characters, then left to right along the bottom line with n2​ characters, and finally bottom-up along the vertical line with n3​ characters. And more, we would like U to be as squared as possible -- that is, it must be satisfied that n1​=n3​=max { k | k≤n2​ for all 3≤n2​≤N } with n1​+n2​+n3​−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

题解：

#include <bits/stdc++.h>

int main() {
    std::string str;
    std::cin >> str;
    int N = str.length();
    int n1 =(N + 2) / 3, n3 = n1;
    int n2 = N + 2 - 2 * n1;
    int left = 0, right = str.length() - 1;
    while(left < n1 - 1) {
        std::cout << str[left++];
        for(int j = 0; j < n2 - 2; j++) {
            std::cout << " ";
        }
        std::cout << str[right--] << std::endl;
    }

    for(int i = left; i <= right; i++) {
        std::cout << str[i];
    }

    return 0;
}