java: add «885. Spiral Matrix III»

Signed-off-by: Matej Focko <me@mfocko.xyz>

java/spiral-matrix-iii.java

@@ -0,0 +1,41 @@
+class Solution {
+  private record Coord(int x, int y) {
+    public void assign(int[] coord) {
+      coord[0] = y;
+      coord[1] = x;
+    }
+
+    public Coord add(Coord rhs) {
+      return new Coord(x + rhs.x, y + rhs.y);
+    }
+  }
+
+  private static final List<Coord> DIRECTIONS =
+      Arrays.asList(new Coord(1, 0), new Coord(0, 1), new Coord(-1, 0), new Coord(0, -1));
+
+  private boolean inBounds(int rows, int cols, Coord pos) {
+    return pos.y() >= 0 && pos.y() < rows && pos.x() >= 0 && pos.x() < cols;
+  }
+
+  public int[][] spiralMatrixIII(int rows, int cols, int rStart, int cStart) {
+    int[][] matrix = new int[rows * cols][2];
+
+    var pos = new Coord(cStart, rStart);
+    for (int i = 0, step = 1, direction = 0; i < matrix.length; ++step) {
+      for (int j = 0; j < 2; ++j) {
+        for (int k = 0; k < step; ++k) {
+          if (inBounds(rows, cols, pos)) {
+            pos.assign(matrix[i]);
+            ++i;
+          }
+
+          pos = pos.add(DIRECTIONS.get(direction));
+        }
+
+        direction = (direction + 1) % 4;
+      }
+    }
+
+    return matrix;
+  }
+}