Count Servers that Communicate.java

// Runtime: 24 ms (Top 15.77%) | Memory: 68.5 MB (Top 7.89%)
class Solution {
    int []parent;
    int []rank;
    public int countServers(int[][] grid) {
        parent=new int[grid.length*grid[0].length];
        rank=new int[grid.length*grid[0].length];
        for(int i=0;i<parent.length;i++){
            parent[i]=i;
            rank[i]=0;
        }
        for(int i=0;i<grid.length;i++){
            for(int j=0;j<grid[0].length;j++){
                if(grid[i][j]==1){
                    check(i,j,grid);
                }
            }
        }
        int count=0;
        for(int i=0;i<parent.length;i++){
            if(parent[i]!=i||rank[i]>0){
              count++;
            }
        }
        return count;
    }
    public void check(int sr,int sc,int [][]grid){
       int mbox=sr*grid[0].length+sc;
        for(int i=sr;i<grid.length;i++){
            if(grid[i][sc]==1){
                int cbox=i*grid[0].length+sc;
                int xl=find(mbox);
                int yl=find(cbox);
                if(xl!=yl){
                    union(xl,yl);
                }
            }
        }
        for(int j=sc;j<grid[0].length;j++){
            if(grid[sr][j]==1){
                int cbox=sr*grid[0].length+j;
                int xl=find(mbox);
                int yl=find(cbox);
                if(xl!=yl){
                    union(xl,yl);
                }
            }
        }
    }
    int find(int x){
        if(parent[x]==x){
            return x;
        }else{
            parent[x]=find(parent[x]);
            return parent[x];
        }
    }
    void union(int x,int y){
        if(rank[x]>rank[y]){
            parent[y]=x;
        }else if(rank[y]>rank[x]){
            parent[x]=y;
        }else{
            parent[x]=y;
            rank[y]++;
        }
    }
}