HDU 1162 Eddy's picture (最小生成树)(java版)

Eddy's picture

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1162

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题目大意：

给你N个点，求把这N个点连在一起的最短总距离。

思路：

假设每两两点之间都有路径，求最小生成树。

AC代码：（Java）

import java.util.Scanner;
import java.math.*;
public class Main {
    public static final int MAXN = 110;
    public static double mp[][] = new double[MAXN][MAXN];
    public static Point p[] = new Point[MAXN]; 
    public static int n;
    public static String answer = new String();
    public static Scanner scn = new Scanner(System.in);
    public static void main(String[] args){
        for (int i = 0; i < MAXN; i++){
            p[i] = new Point();
        }
        while (scn.hasNext()) {
            n = scn.nextInt();
        foundMap();
        answer = String.format("%.2f", prim());
        System.out.println(answer);
        }
        System.exit(0);
    }
    public static boolean foundMap() {
        double x,y;
        for (int i = 0; i < n; i++) {
            x = scn.nextDouble();
            y = scn.nextDouble();
            p[i].setPoint(x, y);
        }//Found points
        for (int i = 0; i < n; i++)
            for (int j = 0; j < n; j++)
                if (i != j)
                    mp[i][j] = Point.getDistencs(p[i], p[j]);
        //Found map
        return true;
    }
    public static double prim() {
        int tempI;
        double tempClos;
        double[] closEdge = new double[MAXN];
        double sum = 0.0;
        //Init closeEdge
        closEdge[0] = 0.0;
        for (int i = 1; i < n; i++) {
            closEdge[i] = mp[0][i];
        }
        //Find n-1 edge
        for (int i = 1; i < n; i++) {
            tempI = -1;
            tempClos = -1.0;
            for (int j = 0; j < n; j++) {
                if (closEdge[j] != 0.0 && (tempClos == -1.0 || closEdge[j] < tempClos)){
                    tempClos = closEdge[j];
                    tempI = j;
                }
            }
            sum += tempClos;
            closEdge[tempI] = 0;
            for (int j = 0; j < n; j++) {
                if (j != tempI && closEdge[j] > mp[tempI][j]) {
                    closEdge[j] = mp[tempI][j];
                }
            }
        }
        return sum;
    }
}
class Point { //已下为一个点类 可以不看。
    private double x;
    private double y;
    public Point(double x,double y) {
        this.x = x;
        this.y = y;
    }
    public Point() {
        x = 0.0;
        y = 0.0;
    }
    public void setPoint(double X,double Y) {
        this.x = X;
        this.y = Y;
    }
    public double getX() {
        return x;
    }
    public double getY() {
        return y;
    }
    public static double getDistencs(Point p1,Point p2) {
        return Math.sqrt(Math.pow(p1.getX() - p2.getX(), 2.0) + Math.pow(p1.getY() - p2.getY(),2.0));
    }
}

2017-07-23 13:07:39