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 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

IDEA

1.首先求出行y，与列x，注意y<=x，且y最接近x

2.控制输出格式，空格数等

CODE

#include<iostream>
#include<cstring>
using namespace std;
int main(){
	string s;
	cin>>s;
	int n=s.length();
	int x,y;
	for(int i=(n+2)/3;i<=n;i++){
		if(i>=3){
			if((n-i+2)%2==0){
				x=i;
				y=(n-i+2)/2;
				if(y<=x){
					break;
				}
			}
		}
	}
	//cout<<x<<" "<<y;
	for(int i=0;i<(n-y+1);i++){
		if(i>=0&&i<y-1){
			cout<<s[i];
			for(int k=0;k<x-2;k++){
				cout<<" ";
			}
			cout<<s[n-1-i]<<endl;
		}else{
			cout<<s[i];
		}
	}
	return 0;
}