class Solution {
    public int minCostConnectPoints(int[][] points) {
        if(points.length==1)return 0;
        int nums[]=new int[points.length];
        for(int i=0;i<nums.length;i++){
            nums[i]=i;
        }
        List<int[]>edges=new ArrayList<>();
        for(int i=0;i<points.length;i++){
            for(int j=i+1;j<points.length;j++){
                int cost=cal(points[i][0],points[j][0],points[i][1],points[j][1]);
                edges.add(new int[]{i,j,cost});
            }
        }
        int res=0;
        Collections.sort(edges,(a,b)->{
            return a[2]-b[2];
        });
        
        for(int pair[]:edges){
            
            int v1=pair[0];
            int v2=pair[1];
            int r1=find(nums,v1);
            int r2=find(nums,v2);
            if(r1==r2)continue;
            nums[r1]=r2;
            res+=pair[2];
           // System.out.println(v1+"  "+v2+"  "+pair[2]);
        }
        
        return res;
    }
    
    public int cal(int x1,int x2,int y1,int y2){
        return Math.abs(x1-x2)+Math.abs(y1-y2);
    }
    
    public int find(int nums[],int x){//union find => find method
		if(nums[x]==x)return x;
		int root=find(nums,nums[x]);
		nums[x]=root;
		return root;
	}
}