并查集的实现【学习算法】

package test1;// 并查集模版(牛客)
// 路径压缩 + 小挂大
// 测试链接 : https://www.nowcoder.com/practice/e7ed657974934a30b2010046536a5372
// 请同学们务必参考如下代码中关于输入、输出的处理
// 这是输入输出处理效率很高的写法
// 提交以下的code，提交时请把类名改成"Main"，可以直接通过
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
class Code01_UnionFindNowCoder {
    public static int MAXN = 1000001;
    public static int[] father = new int[MAXN];
    public static int[] size = new int[MAXN];
    public static int[] stack = new int[MAXN];
    public static int n;
    public static void build() {
        for (int i = 0; i <= n; i++) {
            father[i] = i;
            size[i] = 1;
        }
    }
    // i号节点，往上一直找，找到代表节点返回！
    public static int find(int i) {
        // 沿途收集了几个点
        int size = 0;
        while (i != father[i]) {
            stack[size++] = i;
            i = father[i];
        }
        // 沿途节点收集好了，i已经跳到代表节点了
        while (size > 0) {
            father[stack[--size]] = i;
        }
        return i;
    }
    public static boolean isSameSet(int x, int y) {
        return find(x) == find(y);
    }
    public static void union(int x, int y) {
        int fx = find(x);
        int fy = find(y);
        if (fx != fy) {
            // fx是集合的代表：拿大小
            // fy是集合的代表：拿大小
            if (size[fx] >= size[fy]) {
                size[fx] += size[fy];
                father[fy] = fx;
            } else {
                size[fy] += size[fx];
                father[fx] = fy;
            }
        }
    }
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StreamTokenizer in = new StreamTokenizer(br);
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        while (in.nextToken() != StreamTokenizer.TT_EOF) {
            n = (int) in.nval;
            build();
            in.nextToken();
            int m = (int) in.nval;
            for (int i = 0; i < m; i++) {
                in.nextToken();
                int op = (int) in.nval;
                in.nextToken();
                int x = (int) in.nval;
                in.nextToken();
                int y = (int) in.nval;
                if (op == 1) {
                    out.println(isSameSet(x, y) ? "Yes" : "No");
                } else {
                    union(x, y);
                }
            }
        }
        out.flush();
        out.close();
        br.close();
    }
}