POJ 2082 Terrible Sets - 源代码 - 博客频道 - CSDN.NET


题目链接
Let N be the set of all natural numbers {0 , 1 , 2 , . . . }, and R be the set of all real numbers. wi, hi for i = 1 . . . n are some elements in N, and w0 = 0.
Define set B = {< x, y > | x, y ∈ R and there exists an index i > 0 such that 0 <= y <= hi ,∑0<=j<=i-1wj <= x <= ∑0<=j<=iwj}
Again, define set S = {A| A = WH for some W , H ∈ R+ and there exists x0, y0 in N such that the set T = { < x , y > | x, y ∈ R and x0 <= x <= x0 +W and y0 <= y <= y0 + H} is contained in set B}.
Your mission now. What is Max(S)?
Wow, it looks like a terrible problem. Problems that appear to be terrible are sometimes actually easy.
But for this one, believe me, it's difficult.
Input
The input consists of several test cases. For each case, n is given in a single line, and then followed by n lines, each containing wi and hi separated by a single space. The last line of the input is an single integer -1, indicating the end of input. You may assume that 1 <= n <= 50000 and w1h1+w2h2+...+wnhn < 109.
题目大意:
        若干矩形相互紧挨着在一条轴线上排成一排,求这些矩形所覆盖的区域中面积最大的矩形,输出其面积。
        !!!和POJ 2559类同(只不过其每个矩形的底边长都是1)。
        其中,矩形数不超过50000,所有矩形面积之和不超过10^9,多个测例(题中给出数目),以矩形个数为-1结束测例退出程序。

  1. struct  Rec {//Rectangle,矩形  
  2.     int     w;//width,宽  
  3.     int     h;//height,长  
  4. };  
  5. int  
  6. main() {  
  7.     int     n;//矩形个数  
  8.     int     i;//计数变量  
  9.     int     w_tmp;//temporary width,宽度临时变量  
  10.     int     s_tmp;//面积临时变量  
  11.     int     ans;//answer,最终结果  
  12.     Rec             rec;//临时矩形,用于接收输入的矩形  
  13.     stack<Rec>        stk;//stack,存放矩形的栈  
  14.     while ( scanf("%d", &n), n != -1 ) {  
  15.         ans = 0;//在每个测例的开始都将结果初始化  
  16.         for ( i = 1; i <= n; i++ ) {  
  17.             scanf("%d%d", &rec.w, &rec.h);  
  18.             //保持栈中的矩形高度递增  
  19.             //若待入栈的矩形高度不满足入栈后高度递增的要求则需要  
  20.               //将前面高度比它大的矩形一个个削得跟它一样大  
  21.               //最后再将它们合并成一个矩形  
  22.             //每削一个矩形都需要记录一下该矩形的面积,将比ans大的面积  
  23.               //更新给ans,削完后再跟前面的矩形合并成一个矩形  
  24.             //待削到满足递增要求后再将经过一系列合并后的矩形和  
  25.               //待入栈的矩形合并成一个矩形后入栈  
  26.             w_tmp = 0;//初始化  
  27.             while ( !stk.empty() && rec.h <= stk.top().h ) {  
  28.             //栈非空且入栈矩形高度过低,则需要削前面矩形的头  
  29.                 w_tmp   +=  stk.top().w;//和前一个矩形合并(底边相加)  
  30.                 s_tmp   =   w_tmp * stk.top().h;//高度统一(和前面较矮的看齐)
  31.                 if ( s_tmp > ans )  
  32.                     ans = s_tmp;//动态更新  
  33.                 stk.pop();//合并后将前一个弹栈,再检查更前面的一个矩形  
  34.             }  
  35.             //削完后和待入栈的矮矩形合并后入栈  
  36.             rec.w += w_tmp;//底边相加,高度和入栈矩形看齐  
  37.             stk.push(rec);//合并后压栈  
  38.         }  
  39.         //所有矩形不管削头合并过还是没有削头合并过都已经全部入栈了  
  40.         //现在就用上面用过的方法逐一对高度递增的矩形序列削头合并  
  41.         //动态更新ans后就可以得到最大的面积值了  
  42.         w_tmp = 0;  
  43.         while ( !stk.empty() ) {  
  44.             w_tmp   +=  stk.top().w;  
  45.             s_tmp   =   w_tmp * stk.top().h;  
  46.             if ( s_tmp > ans )  
  47.                 ans = s_tmp;  
  48.             stk.pop();  
  49.         }  
  50.         printf("%d\n", ans);  
  51.     }  
  52.     return 0;  
  53. }  
Also check http://www.cnblogs.com/hxsyl/archive/2012/08/16/2643015.html
Read full article from POJ 2082 Terrible Sets - 源代码 - 博客频道 - CSDN.NET

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