public class Percolation {
   public Percolation(int N)                // create N-by-N grid, with all sites initially blocked
   public void open(int row, int col)       // open the site (row, col) if it is not open already
   public boolean isOpen(int row, int col)  // is the site (row, col) open?
   public boolean isFull(int row, int col)  // is the site (row, col) full?
   public int numberOfOpenSites()           // number of open sites
   public boolean percolates()              // does the system percolate?
}

public class WeightedQuickUnionUF {
   public WeightedQuickUnionUF(int n)      // creates a UF with n elements
   public int count()                      // number of disjoint sets
   public int find(int p)                  // the root of p's set
   public boolean connected(int p, int q)  // whether p and q are in the same set
   public void union(int p, int q)         // join p and q's sets together
}

if(row==0){
    uf.union(top,idx);
    ufFull.union(top, idx);

}
if(row==size-1) uf.union(bottom,idx);

public boolean isFull(int row, int col) {
    if (!valid(row, col)) throw new IndexOutOfBoundsException();
    if(!isOpen(row,col)) return false;
    int idx = convert(row, col);
    return ufFull.connected(top,idx);
}

top =size*size;
bottom = size*size+1;

public int[][] grid; // 存储方格是被阻挡还是被挖空
public int open; // 存储挖空数量
public int size = 0; // 记录尺寸
private WeightedQuickUnionUF uf; // 记录是否渗透的并查集
private WeightedQuickUnionUF ufFull; // 记录某格是否填满的并查集
private int[] dx = {0,0,1,-1};
private int[] dy = {1,-1,0,0};
private int top;
private int bottom;

public Percolation(int N) {
    if(N<=0){
        throw new IllegalArgumentException();
    }
    grid = new int[N][N];
    open = 0;
    size = N;
    top =size*size;
    bottom = size*size+1;
    uf = new WeightedQuickUnionUF(size*size+2);
    ufFull = new WeightedQuickUnionUF(size*size+1);

    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            grid[i][j] = 1;
        }
    }
}

public void open(int row, int col) {
    if (!valid(row, col)) throw new IndexOutOfBoundsException();
    if (isOpen(row, col)) return;
    grid[row][col] = 0;
    open++;
    int idx = convert(row, col);
    if(row==0){
        uf.union(top,idx);
        ufFull.union(top, idx);

    }
    if(row==size-1) uf.union(bottom,idx);
    for (int i = 0; i<4;i++){

        int nr = row+dx[i];
        int nc = col+dy[i];
        if(nr < 0 ||nr>size-1|| nc < 0 ||nc>size-1) continue;
        if (isOpen(nr,nc)){
            int tidx = convert(nr,nc);
            uf.union(idx, tidx);
            ufFull.union(idx, tidx);
        }
    }

}

public boolean isFull(int row, int col) {
    if (!valid(row, col)) throw new IndexOutOfBoundsException();
    if(!isOpen(row,col)) return false;
    int idx = convert(row, col);
    return ufFull.connected(top,idx);
}

public boolean percolates() {
    return uf.connected(top,bottom);
}