| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 5303 | Accepted: 2297 |
Description
A lattice point is an ordered pair (x, y) where x and y are both integers. Given the coordinates of the vertices of a triangle (which happen to be lattice points), you are to count the number of lattice points which lie completely inside of the triangle (points on the edges or vertices of the triangle do not count).
Input
The input test file will contain multiple test cases. Each input test case consists of six integers x1, y1, x2, y2, x3, and y3, where (x1, y1), (x2, y2), and (x3, y3) are the coordinates of vertices of the triangle. All triangles in the input will be non-degenerate (will have positive area), and ?15000 ≤ x1, y1, x2, y2, x3, y3 ≤ 15000. The end-of-file is marked by a test case with x1 = y1 = x2 = y2 = x3 = y3 = 0 and should not be processed.
Output
For each input case, the program should print the number of internal lattice points on a single line.
Sample Input
0 0 1 0 0 1
0 0 5 0 0 5
0 0 0 0 0 0
Sample Output
0
6
Source
#include <cstdio>
#include <cmath>
int abs(int x)
{
return x > 0 ? x : -x;
}
int gcd(int a, int b)
{
return b ? gcd(b, a % b) : a;
}
int main()
{
int x1, y1, x2, y2, x3, y3;
while(scanf("%d %d %d %d %d %d", &x1, &y1, &x2, &y2, &x3, &y3) != EOF)
{
if(x1 == 0 && y1 == 0 && x2 == 0 && y2 == 0 && x3 == 0 && y3 == 0)
break;
int x12 = abs(x1 - x2);
int y12 = abs(y1 - y2);
int x13 = abs(x1 - x3);
int y13 = abs(y1 - y3);
int x23 = abs(x2 - x3);
int y23 = abs(y2 - y3);
printf("%d\n", abs(((x2-x1) * (y3-y1) - (x3-x1) * (y2-y1)) / 2) + 1 - (gcd(x12,y12) + gcd(x13,y13) + gcd(x23,y23)) / 2);
}
}
POJ 2954 Triangle (皮克定理, 三角形叉乘求面积)
原文地址：http://blog.csdn.net/tc_to_top/article/details/43423461
