UVA - 10250
| Time Limit: 3000MS | Memory Limit: Unknown | 64bit IO Format: %lld & %llu |
Description
Problem E
The Other Two Trees
Input: standard input
Output: standard output
Time Limit: 2 seconds
You have a quadrilateral shaped land whose opposite fences are of equal length. You have four neighbors whose lands are exactly adjacent to your four fences, that means you have a common fence with all of them. For example if you have a fence of length d in
one side, this fence of length d is also the fence of the adjacent neighbor on that side. The adjacent neighbors have no fence in common among themselves and their lands also don’t intersect. The main difference between their land and your
land is that their lands are all square shaped. All your neighbors have a tree at the center of their lands. Given the Cartesian coordinates of trees of two opposite neighbors, you will have to find the Cartesian coordinates of the other two trees.
Input
The input file contains several lines of input. Each line contains four floating point or integer numbers x1, y1, x2, y2, where (x1, y1), (x2, y2) are the coordinates of the trees of two opposite neighbors. Input is terminated
by end of file.
Output
For each line of input produce one line of output which contains the line “Impossible.” without the quotes, if you cannot determine the coordinates of the other two trees. Otherwise, print four floating point numbers separated by a single
space with ten digits after the decimal point ax1, ay1, ax2, ay2, where (ax1, ay1) and (ax2, ay2) are the coordinates of the other two trees. The output will be checked with special judge program, so don’t
worry about the ordering of the points or small precision errors. The sample output will make it clear.
Sample Input
10 0 -10 0
10 0 -10 0
10 0 -10 0
Sample Output
0.0000000000 10.0000000000 0.0000000000 -10.0000000000
0.0000000000 10.0000000000 -0.0000000000 -10.0000000000
0.0000000000 -10.0000000000 0.0000000000 10.0000000000
(World Final Warm-up Contest, Problem Setter: Shahriar Manzoor)
Source
Root :: Prominent Problemsetters :: Shahriar Manzoor
Root :: AOAPC I: Beginning Algorithm Contests (Rujia Liu) :: Volume 1. Elementary Problem Solving :: Maths - Simple Geometry
Root :: Competitive Programming 3: The New Lower Bound of Programming Contests (Steven & Felix Halim) :: (Computational) Geometry :: Basic Geometry ::Points
and Lines
题意： 就是给你正方形两个对顶顶点的坐标，求另外两个顶点的坐标
AC代码：
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
int main()
{
double x1, y1, x2, y2;
while(scanf("%lf %lf %lf %lf", &x1, &y1, &x2, &y2)!=EOF)
{
if(fabs(x1-x2)<1e-7 && fabs(y1-y2)<1e-7)
{
printf("Impossible.\n");
continue;
}
double midx, midy, x3, y3, x4, y4, t1, t2, k;
midx = (x1 + x2) / 2; midy = (y1 + y2) / 2;
t1 = (x1 - midx)*(x1 - midx) + (y1 - midy)*(y1 - midy);
k = (y1-y2)/(x1-x2); //对定点组成直线的斜率
t2 = t1 / (k*k + 1);
x3 = midx - k*sqrt(t2); x4 = midx + k*sqrt(t2);
y3 = midy + sqrt(t2); y4 = midy - sqrt(t2);
printf("%.10lf %.10lf %.10lf %.10lf\n", x3, y3, x4, y4);
}
return 0;
}