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

Posted 2020-09-29 Wei_Xiong

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）

 1 import java.util.Scanner;
 2 import java.math.*;
 3 public class Main {
 4     public static final int MAXN = 110;
 5     public static double mp[][] = new double[MAXN][MAXN];
 6     public static Point p[] = new Point[MAXN]; 
 7     public static int n;
 8     public static String answer = new String();
 9     public static Scanner scn = new Scanner(System.in);
10     public static void main(String[] args){
11         for (int i = 0; i < MAXN; i++){
12             p[i] = new Point();
13         }
14         while (scn.hasNext()) {
15             n = scn.nextInt();
16         foundMap();
17         answer = String.format("%.2f", prim());
18         System.out.println(answer);
19         }
20         System.exit(0);
21     }
22     public static boolean foundMap() {
23         double x,y;
24         for (int i = 0; i < n; i++) {
25             x = scn.nextDouble();
26             y = scn.nextDouble();
27             p[i].setPoint(x, y);
28         }//Found points
29         for (int i = 0; i < n; i++)
30             for (int j = 0; j < n; j++)
31                 if (i != j)
32                     mp[i][j] = Point.getDistencs(p[i], p[j]);
33         //Found map
34         return true;
35     }
36     public static double prim() {
37         int tempI;
38         double tempClos;
39         double[] closEdge = new double[MAXN];
40         double sum = 0.0;
41         //Init closeEdge
42         closEdge[0] = 0.0;
43         for (int i = 1; i < n; i++) {
44             closEdge[i] = mp[0][i];
45         }
46         //Find n-1 edge
47         for (int i = 1; i < n; i++) {
48             tempI = -1;
49             tempClos = -1.0;
50             for (int j = 0; j < n; j++) {
51                 if (closEdge[j] != 0.0 && (tempClos == -1.0 || closEdge[j] < tempClos)){
52                     tempClos = closEdge[j];
53                     tempI = j;
54                 }
55             }
56             sum += tempClos;
57             closEdge[tempI] = 0;
58             for (int j = 0; j < n; j++) {
59                 if (j != tempI && closEdge[j] > mp[tempI][j]) {
60                     closEdge[j] = mp[tempI][j];
61                 }
62             }
63         }
64         return sum;
65     }
66 }
67 class Point { //已下为一个点类 可以不看。
68     private double x;
69     private double y;
70     public Point(double x,double y) {
71         this.x = x;
72         this.y = y;
73     }
74     public Point() {
75         x = 0.0;
76         y = 0.0;
77     }
78     public void setPoint(double X,double Y) {
79         this.x = X;
80         this.y = Y;
81     }
82     public double getX() {
83         return x;
84     }
85     public double getY() {
86         return y;
87     }
88     public static double getDistencs(Point p1,Point p2) {
89         return Math.sqrt(Math.pow(p1.getX() - p2.getX(), 2.0) + Math.pow(p1.getY() - p2.getY(),2.0));
90     }
91 }

2017-07-23 13:07:39