[백준 알고리즘] 1004번 어린왕자 (java)

[백준 알고리즘] 1004번 어린왕자 (java)

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1. 피드백

• 처음에 좌표 대소 비교로 풀었는데 복잡하고 식을 잘못 생각함.
• 거리 비교로 다시 품.

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2. Source

import java.util.Scanner;

public class Num1004
{
    public static void main(String [] args)
    {
        Scanner sc = new Scanner(System.in);
        int T = sc.nextInt();
        int x1, y1, x2, y2, n, count = 0;
        Planet planet;
        for (int i = 0 ; i < T ; i++)
        {
            count = 0;

            x1 = sc.nextInt();
            y1 = sc.nextInt();
            x2 = sc.nextInt();
            y2 = sc.nextInt();

            n = sc.nextInt();

            for (int j = 0 ; j < n ; j++)
            {
                planet = new Planet(sc.nextInt(), sc.nextInt(), sc.nextInt());
                count += solve(x1, y1, x2, y2, planet);
            }
            System.out.println(count);
        }
    }

    public static int solve(int x1, int y1, int x2, int y2, Planet planet)
    {
        int d1 = (planet.cx - x1) * (planet.cx - x1) + (planet.cy - y1) * (planet.cy - y1);
        int d2 = (planet.cx - x2) * (planet.cx - x2) + (planet.cy - y2) * (planet.cy - y2);

        int r = planet.r * planet.r;
        if ( (d1 > r && d2 < r) || (d1 < r && d2 > r) )
            return 1;
        else
            return 0;
    }
}

class Planet
{
    int cx;
    int cy;
    int r;

    public Planet(int cx, int cy, int r)
    {
        this.cx = cx;
        this.cy = cy;
        this.r = r;
    }
}