CodeForces 1216C (sham + computational geometry scan line)

 

Portal

 

• the meaning of problems

　　Give you three rectangles are numbered 1, 2;

　　Determining whether the rectangle is a rectangle, and a rectangular 2 3 completely covered;

　　If not completely cover, output "YES", on the contrary, the output "NO";

•answer

　　I used to do a scan line;

　　First, the data structure is defined as follows:

 1 struct Data
 2 {
 3     int x;
 4     int y1,y2;
 5     int f;
 6     int id;
 7     bool operator < (const Data& obj)const
 8     {
 9         return x < obj.x;
10     }
11 }line[10],white[2];

　　To scan a vertical side;

　　These three rectangular left and right side respectively stored in said data structure;

　　1 and save approximately rectangular sides;

. 1  int NUM = 0 ;
 2  for ( int I = . 1 ; I <= . 3 ; ++ I)
 . 3  {
 . 4      int X1, Y1;
 . 5      int X2, Y2;
 . 6      Scanf ( " % D%% D D D% " , & X1, & Y1, & X2, & Y2);
 . 7          
. 8      IF (I == . 1 )
 . 9      {
 10          White [ 0 ] = {X1, Y1, Y2, . 1 , I}; /// F =. 1 indicates that the edge is left of the current rectangle, f = -1 indicates that the edge is right of the current rectangle 
. 11          White [ . 1] = {X2, Y1, Y2, - 1 , I}; /// two vertical edges of a storage matrix
 12 is      }
 13 is      Line [NUM ++] = {X1, Y1, Y2, a , I}; / // save the vertical side of the matrix
 14      Line [NUM ++] = {X2, Y1, Y2, - . 1 , I};
 15 }

　　After a good edge information is stored, arranged in ascending order of x;

　　The next step is determining whether the rectangle is completely covered by 3 sides of a vertical rectangle;

　　However, only a vertical edge is determined whether it is not enough to completely cover, but also need to scan a horizontal edge;

　　The reason you can simulate what the following examples:

0 0 4 4
0 0 4 2
0 3 4 4

　　In this case, we have the need to preserve the rectangle on the bottom, and scan it again again;

　　Only when vertical sides and horizontal sides of the rectangle 1 are completely covered 2,3 are rectangular, the rectangle can be described by a rectangle entirely covering the 2,3;

•Code

　　CodeForces1216C.cpp

• Wa off sample

10 10 11 11
10 10 11 11
10 10 11 11

　　This example illustrates a very clear statement determines the placement of the Code 49 to line 50 and how to determine the condition judgment;

　　There is a solution to a problem in the above examples clearly illustrates why to be scanned twice;