题解 | #Hello World for U#

#include<iostream>
#include<cstring>
using namespace std;
int main()
{
	char str[100] = {'\0'};          //初始化
	while (cin>>str)              //配合键盘的ctrl+Z，然后回车，从而停止输入
	{
		int len = strlen(str);     //字符串长度
		if (len < 5)
		{
			cout << "字符串长度应大于等于5，请重新输入字符串！"<<endl;
			continue;
		}

		//用暴力枚举法确定n1,n2,n3
		int n1 = 0;
		int n2;
		int n3 = 0;
		for (n2 = 3; n2 <= len; n2++)
		{
			if ((len + 2 - n2) % 2 == 0)         //因为n1 + n2 + n3 - 2 = len，且n1,n2,n3都得是整数
			{
				n1 = (len + 2 - n2) / 2;      
			}
			else
			{
				continue;
			}

			if (n1 > n2)
			{
				continue;      //不符合“n1必须小于等于n2”这个条件
			}
			else if (n1 <= n2)
			{
				break;         //此时的n1一定是符合题意的n1的最大值
			}
			n3 = n1;
		}

		//在二维字符数组中填充U型字符
		char arr[100][100];      //初始化
		for (int i = 0; i < 100; i++)
			for (int j = 0; j < 100; j++)
				arr[i][j] = ' ';
		int idx = 0;                      //显示当前处于字符串str[]的什么位置
		for (int i = 0; i < n1; i++)          //填充n1列
			arr[i][0] = str[idx++];
		for (int j = 1; j < n2; j++)
			arr[n1 - 1][j] = str[idx++];      //填充n2行
		for (int i = n1 - 2; i >= 0; i--)
			arr[i][n2 - 1] = str[idx++];       //填充n3列

		//打印输出
		for (int i = 0; i < n1; i++)
		{
			for (int j = 0; j < n2; j++)
			{
				cout << arr[i][j];
			}
			cout << endl;
		}
	}
	return 0;
}