Hw2

hw2/src/Percolation.java

@@ -2,37 +2,86 @@
 
 
 public class Percolation {
-    // TODO: Add any necessary instance variables.
+    int N;
+    boolean[][] grid;
+    int numberOfOpenSites = 0;
+    WeightedQuickUnionUF uf;
+    WeightedQuickUnionUF ufFull; // Used to prevent backwash in isFull
+    int virtualTop;
+    int virtualBottom;
 
     public Percolation(int N) {
-        // TODO: Fill in this constructor.
+        if (N <= 0) {
+            throw new IllegalArgumentException("Class should be constructed with a value greater than 0");
+        }
+        this.N = N;
+        grid = new boolean[N][N];
+        uf = new WeightedQuickUnionUF(N * N + 2);
+        ufFull = new WeightedQuickUnionUF(N * N + 1);
+        virtualTop = N * N;
+        virtualBottom = N * N + 1;
     }
 
     public void open(int row, int col) {
-        // TODO: Fill in this method.
+        validateIndices(row, col);
+        grid[row][col] = true;
+        numberOfOpenSites++;
+
+        int p = rcToIndex(row, col);
+
+        if (row == 0) {
+            uf.union(p, virtualTop);
+            ufFull.union(p, virtualTop);
+        }
+        if (row == N - 1) uf.union(p, virtualBottom);
+
+        if (row > 0 && isOpen(row - 1, col)) {
+            int q = rcToIndex(row - 1, col); // top
+            uf.union(p, q);
+            ufFull.union(p, q);
+        }
+        if (row < N - 1 && isOpen(row + 1, col)) {
+            int q = rcToIndex(row + 1, col); // bottom
+            uf.union(p, q);
+            ufFull.union(p, q);
+        }
+        if (col > 0 && isOpen(row, col - 1)) {
+            int q = rcToIndex(row, col - 1); // left
+            uf.union(p, q);
+            ufFull.union(p, q);
+        }
+        if (col < N - 1 && isOpen(row, col + 1)) {
+            int q = rcToIndex(row, col + 1); // right
+            uf.union(p, q);
+            ufFull.union(p, q);
+        }
     }
 
     public boolean isOpen(int row, int col) {
-        // TODO: Fill in this method.
-        return false;
+        validateIndices(row, col);
+        return grid[row][col];
     }
 
     public boolean isFull(int row, int col) {
-        // TODO: Fill in this method.
-        return false;
+        validateIndices(row, col);
+        int p = rcToIndex(row, col);
+        return ufFull.connected(virtualTop, p);
     }
 
     public int numberOfOpenSites() {
-        // TODO: Fill in this method.
-        return 0;
+        return numberOfOpenSites;
     }
 
     public boolean percolates() {
-        // TODO: Fill in this method.
-        return false;
+        return uf.connected(virtualTop, virtualBottom);
+    }
+    private void validateIndices(int row, int col) {
+        if (row < 0 || row >= N || col < 0 || col >= N) {
+            throw new IndexOutOfBoundsException("Index out of bounds");
+        }
     }
 
-    // TODO: Add any useful helper methods (we highly recommend this!).
-    // TODO: Remove all TODO comments before submitting.
-
+    private int rcToIndex(int row, int col) {
+        return row * N + col;
+    }
 }