Java HdAcm1174

空间一般直线的方程是:
(x-x0)/a=(y-y0)/b=(z-z0)/c,
这是一条过(x0,y0,z0),方向矢量为{a,b,c}的直线.

假设已知点的坐标是A(e,f,g),过A点,且与{a,b,c}垂直的平面是,

a(x-e)+b(y-f)+c(z-g)=0,直线(x-x0)/a=(y-y0)/b=(z-z0)/c,与这个平面的交点是B,

再由两点的距离公式求出AB,即得.

import java.util.Scanner;

public class Main {

public static void main(String[] args) {

Scanner cin = new Scanner(System.in);
int n = cin.nextInt();

while(n != 0){
float[] enemy = new float[5];
for(int i = 0; i < 5; i++){
enemy[i] = cin.nextFloat();
}

float[] soldier = new float[8];
for(int i = 0; i < 8; i++){
soldier[i] = cin.nextFloat();
}

boolean b = hit(enemy, soldier);
if(b){
System.out.println("YES");
}
else {
System.out.println("NO");
}
n--;
}
cin.close();
}

public static boolean hit(float[] enemy, float[] soldier){

//敌人头的中心 h1,r1,x1,y1,z1
float r1 = enemy[1];
//float[] centerEnemyHead = {enemy[2], enemy[3], enemy[0] - enemy[1] + enemy[4]};
//警察瞄准敌人时人头的中心 h2,r2,x2,y2,z2,x3,y3,z3
float h2 = soldier[0];
float r2 = soldier[1];
float height = h2 * 0.9f - r2 ;//实际高度 低 0.1

float[]  direction = {soldier[5], soldier[6], soldier[7]};

float a = direction[0], b = direction[1], c = direction[2];
float x0 = soldier[2], y0 = soldier[3], z0 = soldier[4] + height;
float e = enemy[2], f = enemy[3], g = enemy[0] - enemy[1] + enemy[4];

float fenmu = a*a/b + b + c*c/b;
float fenzi = a*a*y0/b - a*x0 + a*e + b*f + c*c*y0/b - c*z0 +c*g;

float y = fenzi / fenmu;

float x = a*(y - y0)/b + x0;
float z = c*(y - y0)/b + z0;
//两点距离平方
float doubleR = (x-e)*(x-e) + (y-f)*(y-f) + (z-g)*(z-g);

if(doubleR > r1*r1)
return false;
else {
return true;
}

}
}