在 Java 中使用上下图元测试两条线是否相交
原文:https://www . geesforgeks . org/使用-上-下-基元-测试-是否-两条线-在 java 中相交/
上下图元是通过比较线的端点来检查线是否相交的方法。这里有一个 JAVA 程序，它使用上面下面的原语来测试两条线是否相交。只有当一条线的一个端点位于另一条线的左端点的左侧，并且其右端点位于另一条线的右端点的右侧时，该方法才返回 true。
例T0】
接近T0】
下面是上述方法的实现。
爪哇
// This is a java program to find whether two lines
// intersect or not using above and below primitive
public class Main {
public static void check(int x1, int x2, int y1, int y2,
int p1, int p2, int q1, int q2)
{ // Segment of line 1 is stored as a1
int a1 = (y2 - y1) * p1 + (x1 - x2) * q1
+ (x2 * y1 - x1 * y2);
if (a1 < 0) {
// Segment of line 2 is stored as a2
int a2 = (y2 - y1) * p2 + (x1 - x2) * q2
+ (x2 * y1 - x1 * y2);
if (a2 >= 0)
System.out.println("Intersecting");
else if (a2 < 0)
System.out.println("Not intersecting");
}
else if (a1 > 0) {
int a2 = (y2 - y1) * p2 + (x1 - x2) * q2
+ (x2 * y1 - x1 * y2);
if (a2 <= 0)
System.out.println("Intersecting");
else if (a2 > 0)
System.out.println("Not intersecting");
}
// lines are coincinding
else
System.out.println(
"points are lying on the line");
}
// Driver Code
public static void main(String args[])
{
// Taking the coordinates of first line as input
int x1 = 2, y1 = 3;
int x2 = 6, y2 = 4;
// Equation of line using slope point form
System.out.println("Equation 1: (" + (y2 - y1)
+ ")x+(" + (x1 - x2) + ")y+("
+ (x2 * y1 - x1 * y2) + ") = 0");
// Taking the coordinates of second line as input
int p1 = 3, q1 = 4;
int p2 = 7, q2 = 1;
// Equation of line using slope point form
System.out.println("Equation 2: (" + (q2 - q1)
+ ")x+(" + (p1 - p2) + ")y+("
+ (p2 * q1 - p1 * q2) + ") = 0");
check(x1, x2, y1, y2, p1, p2, q1, q2);
}
}
输出
Equation 1: (1)x+(-4)y+(10) = 0
Equation 2: (-3)x+(-4)y+(25) = 0
Intersecting
时间复杂度: O(1)
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