【LeetCode】547.朋友圈(并查集)

题目

547. 朋友圈

代码

class Solution {
    public int findCircleNum(int[][] M) {
        int len = M.length;
        UF uf = new UF(len);
        for(int i = 0; i < len; i++){
            for(int j = 0; j < len; j++){
                if(M[i][j] == 1){
                    uf.union(i, j);
                }
            }
        }
        return uf.getcount();
    }
}
class UF{
    private int count;//连通分量个数
    private int[] parent;
    private int[] size;

    public UF(int n){
        this.count = n;
        parent = new int[n];
        size = new int[n];
        for(int i = 0; i < n; i++){
            parent[i] = i;
            size[i] = 1;
        }
    }
    public void union(int p, int q){
        int rootP = find(p);
        int rootQ = find(q);
        if(rootP == rootQ){
            return;
        }
        //P 结点大于 Q Q接在P下
        if(size[rootP] > size[rootQ]){
            parent[rootQ] = rootP;
            size[rootQ] += size[rootP];
        }else{
            parent[rootP] = rootQ;
            size[rootP] += size[rootQ];
        }
        count--;
    }
    public boolean isConnect(int p, int q){
        int rootP = find(p);
        int rootQ = find(q);
        return rootP == rootQ;
    }
    public int find(int x){
        while(parent[x] != x){
            parent[x] = parent[parent[x]];
            x = parent[x];
        }
        return x;
    }
    public int getcount(){
        return count;
    }
}