【算法】并查集

class UnionFind {
    Integer[] arr;
    public UnionFind(int size) {
        this.arr = new Integer[size];
        for (int i = 1; i < arr.length; i++)
            arr[i] = new Integer(i);
    }
    public int findRoot(int i) {
        while (i != arr[i]) i = arr[i];
        return i;
    }
    public void union(int a, int b) {
        a = findRoot(a);
        b = findRoot(b);
        arr[a] = b;
    }
}