day 55 图论part7

文章目录

• [prim算法精讲 卡码网 53. 寻宝（第七期模拟笔试）](#prim算法精讲 卡码网 53. 寻宝（第七期模拟笔试）)
• [kruskal算法精讲 53. 寻宝（第七期模拟笔试）](#kruskal算法精讲 53. 寻宝（第七期模拟笔试）)

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prim算法精讲 卡码网 53. 寻宝（第七期模拟笔试）

import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int V = sc.nextInt();
        int E = sc.nextInt();
        int[][] grid = new int[V + 1][V + 1];
        for (int i = 0 ; i <= V; i++) {
            Arrays.fill(grid[i], Integer.MAX_VALUE);
        }

        for (int i = 0; i < E; i++) {
            int s = sc.nextInt();
            int t = sc.nextInt();
            grid[s][t] = sc.nextInt();
            grid[t][s] = grid[s][t];
        }

        int[] minDist  = new int[V + 1];
        Arrays.fill(minDist, Integer.MAX_VALUE);
        boolean[] isTree = new boolean[V + 1];
        for (int i = 1; i < V; i++) {
            int minvalue = Integer.MAX_VALUE;
            int cur = 1;
            for (int j = 1; j <= V; j++)  {
                if (!isTree[j] && minDist[j] < minvalue) {
                    minvalue = minDist[j];
                    cur = j;
                }
            }
            isTree[cur] = true;
            for (int j = 1; j <= V; j++) {
                if (isTree[j] == false && grid[cur][j] < minDist[j]) {
                    minDist[j] = grid[cur][j];
                }
            }
        }
        int result = 0;

        for (int i = 2; i <=V; i++) {
            result += minDist[i];
        }
        System.out.println(result);
    }
}

kruskal算法精讲 53. 寻宝（第七期模拟笔试）

import java.util.*;


class Edge {
    int l, r, val;
    public Edge(int l, int r, int val) {
        this.l = l;
        this.r = r;
        this.val = val;
    }
}
class Main {
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int v = sc.nextInt();
        int e = sc.nextInt();
        List<Edge> edges = new ArrayList<>();
        for (int i = 0; i < e; i++) {
            int v1 = sc.nextInt();
            int v2 = sc.nextInt();
            int val = sc.nextInt();
            edges.add(new Edge(v1, v2, val));
        }

        edges.sort(Comparator.comparingInt(edge -> edge.val));
        int res = 0;
        DisJoint disjoint = new DisJoint(v + 1);
        for (Edge edge : edges) {
            int x = disjoint.find(edge.l);
            int y = disjoint.find(edge.r);
            if (x != y) {
                res += edge.val;
                disjoint.join(x, y);
            }
        }
        System.out.println(res);

    }
}

class DisJoint {
    private int[] father;

    public DisJoint(int N) {
        father = new int[N + 1];
        for (int i = 0; i <= N; i++) {
            father[i] = i;
        }
    }
    public int find(int n) {
        return father[n] == n ? n : (father[n] = find(father[n]));
    }

    public void join(int n, int m) {
        n = find(n);
        m = find(m);
        if (n == m) {
            return;
        }
        father[n] = m;
    }

    public boolean isSame(int n, int m) {
        return find(n) == find(m);
    }
}