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package class16;
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// 课上没讲这个实现
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// 因为是一样的，都是用Kruskal算法实现最小生成树，只不过是牛客网的测试数据
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// 测试链接 : https://www.nowcoder.com/questionTerminal/c23eab7bb39748b6b224a8a3afbe396b
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// 请同学们务必参考如下代码中关于输入、输出的处理
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// 这是输入输出处理效率很高的写法
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// 提交以下所有代码，把主类名改成Main，可以直接通过
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.io.OutputStreamWriter;
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import java.io.PrintWriter;
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import java.io.StreamTokenizer;
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import java.util.Arrays;
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public class Code04_KruskalNowCoder {
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public static int MAXM = 100001;
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public static int[][] edges = new int[MAXM][3];
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public static void main(String[] args) throws IOException {
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BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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StreamTokenizer in = new StreamTokenizer(br);
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PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
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while (in.nextToken() != StreamTokenizer.TT_EOF) {
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int n = (int) in.nval;
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in.nextToken();
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int m = (int) in.nval;
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for (int i = 0; i < m; i++) {
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in.nextToken();
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edges[i][0] = (int) in.nval;
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in.nextToken();
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edges[i][1] = (int) in.nval;
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in.nextToken();
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edges[i][2] = (int) in.nval;
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}
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Arrays.sort(edges, 0, m, (a, b) -> a[2] - b[2]);
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build(n);
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int ans = 0;
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for (int[] edge : edges) {
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if (union(edge[0], edge[1])) {
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ans += edge[2];
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}
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}
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out.println(ans);
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out.flush();
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}
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}
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// 下面是并查集结构
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public static int MAXN = 10001;
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public static int[] father = new int[MAXN];
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public static int[] size = new int[MAXN];
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public static int[] help = new int[MAXN];
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public static void build(int n) {
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for (int i = 1; i <= n; i++) {
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father[i] = i;
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size[i] = 1;
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}
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}
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private static int find(int i) {
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int size = 0;
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while (i != father[i]) {
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help[size++] = i;
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i = father[i];
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}
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while (size > 0) {
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father[help[--size]] = i;
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}
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return i;
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}
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// 如果i和j，原本是一个集合，返回false
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// 如果i和j，不是一个集合，合并，然后返回true
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public static boolean union(int i, int j) {
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int fi = find(i);
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int fj = find(j);
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if (fi != fj) {
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if (size[fi] >= size[fj]) {
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father[fj] = fi;
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size[fi] += size[fj];
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} else {
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father[fi] = fj;
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size[fj] += size[fi];
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}
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return true;
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} else {
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return false;
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}
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}
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}
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