spiral-matrix

Author: chjung99

spiral-matrix/chjung99.java

@@ -0,0 +1,68 @@
+class Solution {
+    // right, down, left, up
+    int[] dx = {0, 1, 0, -1};
+    int[] dy = {1, 0, -1, 0};
+    boolean[][] visit;
+
+    int m;
+    int n;
+    public List<Integer> spiralOrder(int[][] matrix) {
+        m = matrix.length;
+        n = matrix[0].length;
+        visit = new boolean[m][n];
+        return bfs(matrix);
+    }
+
+    public boolean outOfRange(int x, int y){
+        return ((x < 0 || x >= m) || (y < 0 || y >= n));
+    }
+
+    public List<Integer> bfs(int[][] matrix) {
+        List<Integer> spiral = new ArrayList<>();
+
+        Queue<Point> q = new ArrayDeque<>();
+
+        int startX = 0;
+        int startY = 0;
+        int startDir = 0;
+
+        q.add(new Point(startX, startY, startDir));
+        visit[startX][startY] = true;
+
+        while (!q.isEmpty()){
+            Point cur = q.poll();
+            spiral.add(matrix[cur.x][cur.y]);
+
+            int nextX = cur.x + dx[cur.dir];
+            int nextY = cur.y + dy[cur.dir];
+            int nextDir = cur.dir;
+
+            if (outOfRange(nextX, nextY) || visit[nextX][nextY]) {
+                nextDir = (nextDir + 1) % 4;
+            }
+
+            nextX = cur.x + dx[nextDir];
+            nextY = cur.y + dy[nextDir];
+
+            if (!outOfRange(nextX, nextY) && !visit[nextX][nextY]){
+                q.add(new Point(nextX, nextY, nextDir));
+                visit[nextX][nextY] = true;
+            }
+        }
+        return spiral;
+    }
+
+    class Point{
+        int x;
+        int y;
+        int dir;
+        public Point(int x, int y, int dir){
+            this.x = x;
+            this.y = y;
+            this.dir = dir;
+        }
+    }
+
+}
+
+