2016huasacm暑假集训训练三 G

题目链接：https://vjudge.net/contest/123674#problem/G

这题和上一道题差不多，还更简单点，直接用prim算法就行，直接贴AC代码：

import java.io.BufferedInputStream;
import java.util.Scanner;

public class Main {
    final static int N = 1 << 20;
    static int n, m, a[][] = new int[105][105], b[] = new int[105], sum;

    public static void main(String[] args) {
        Scanner s = new Scanner(new BufferedInputStream(System.in));
        int u, v, w, i, j;
        while (s.hasNext()) {
            n = s.nextInt();
            if (n == 0)
                break;

            for (i = 1; i <= n; i++)
                for (j = 1; j <= n; j++)
                    a[i][j] = 0;
            m = n * (n - 1) / 2;
            while (m-- > 0) {
                u = s.nextInt();
                v = s.nextInt();
                w = s.nextInt();
                a[u][v] = a[v][u] = w;
            }
            sum = 0;

            prim(1);
            System.out.println(sum);
        }
        s.close();
    }

    static void prim(int u) {
        int i, j, min, v;
        for (i = 1; i <= n; i++) {
            b[i] = a[u][i];
        }
        sum = 0;
        b[u] = -1;
        for (i = 1; i <= n; i++) {
            min = N;
            v = -1;
            for (j = 1; j <= n; j++) {
                if (b[j] != -1 && b[j] < min) {
                    v = j;
                    min = b[j];
                }
            }
            if (v != -1) {
                sum += b[v];
                b[v] = -1;
                for (j = 1; j <= n; j++) {
                    if (b[j] != -1 && a[v][j] < b[j])
                        b[j] = a[v][j];
                }
            }
        }

    }

}