HDOJ 1117 模拟 水

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1117

这题理解题意最重要。一张纸，有正反两面，将这张纸对折，则一面又分成了两个半页。将若干张纸这样对折，并将这些纸堆叠起来，可以得到一本小册子。现在就要为这个小册子的每个半页编号。

下图是小册子只有一张纸时的情况。

#include <iostream>
#include <string>
using namespace std;

const int SHEETS_NUM = 30;

class Sheet
{
public:
    int frontRight, frontLeft, backLeft, backRight;
};

Sheet sheets[SHEETS_NUM];

void initSheets(int sheetsNum)
{
    for (int i = 1;i <= sheetsNum;i ++)
        sheets[i].backLeft = sheets[i].backRight = sheets[i].frontLeft = sheets[i].frontRight = -1;
}

int main ()
{
    int pagesNum;
    while (scanf("%d",&pagesNum) != -1 && pagesNum != 0)
    {
        int sheetsNum;
        sheetsNum = pagesNum / 4;
        if (pagesNum % 4 != 0)
            sheetsNum ++;
        initSheets(sheetsNum);
        int sheetId = 1, pageId;
        //将所有pages叠起来后的右半部分pages编号
        for (pageId = 1;pageId <= (sheetsNum * 2) && pageId <= pagesNum;pageId ++)
        {
            if (pageId % 2 == 1)
                sheets[sheetId].frontRight = pageId;
            else
                sheets[sheetId].backLeft = pageId;
            if (pageId % 2 == 0)
                sheetId ++;
        }
        sheetId = sheetsNum;
        for (pageId = (sheetsNum * 2) + 1;pageId <= pagesNum;pageId ++)
        {
            if (pageId % 2 == 1)
                sheets[sheetId].backRight = pageId;
            else
                sheets[sheetId].frontLeft = pageId;
            if (pageId % 2 == 0)
                sheetId --;
        }
        printf("Printing order for %d pages:\n",pagesNum);
        
        for (int sheetId = 1;sheetId <= sheetsNum;sheetId ++)
        {
            if ( ! (sheets[sheetId].frontLeft == -1 && sheets[sheetId].frontRight == -1) )
            {
                //前面
                printf("Sheet %d, front: ",sheetId);
                if (sheets[sheetId].frontLeft == -1)
                    printf("Blank, ");
                else
                    printf("%d, ",sheets[sheetId].frontLeft);

                if (sheets[sheetId].frontRight == -1)
                    printf("Blank\n");
                else
                    printf("%d\n",sheets[sheetId].frontRight);
            }
            if ( ! (sheets[sheetId].backLeft == -1 && sheets[sheetId].backRight == -1) )
            {
                //背面
                printf("Sheet %d, back : ",sheetId);
                if (sheets[sheetId].backLeft == -1)
                    printf("Blank, ");
                else
                    printf("%d, ",sheets[sheetId].backLeft);

                if (sheets[sheetId].backRight == -1)
                    printf("Blank\n");
                else
                    printf("%d\n",sheets[sheetId].backRight);
            }
        }
    }
    return 0;
}