From 575226707a502a79eb3b090b6fa50443c8922280 Mon Sep 17 00:00:00 2001
From: Tonghann Teng <tengtonghann@gmail.com>
Date: Mon, 23 Mar 2020 23:37:27 -0500
Subject: [PATCH] 8. Spiral Matrix

---
 afteracademy/SpiralMatrix.java | 58 ++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 afteracademy/SpiralMatrix.java

diff --git a/afteracademy/SpiralMatrix.java b/afteracademy/SpiralMatrix.java
new file mode 100644
index 0000000..a0da3a9
--- /dev/null
+++ b/afteracademy/SpiralMatrix.java
@@ -0,0 +1,58 @@
+//  8. Spiral Matrix
+
+class SpiralMatrix {
+
+    public int[] spiralMatrix(int[][] arr) {
+        // write your awesome code here
+        int[] result = new int[arr.length * arr[0].length];
+        int index = 0;
+        int top = 0;
+        int right = arr[0].length - 1; //   4 -1 = 3
+        int down = arr.length - 1; // 3 - 1 = 2
+        int left = 0;
+        while (index < result.length) {
+            for (int i = 0; i < arr[0].length; i++) {
+                if (isValid(arr, top, i)) {
+                    result[index] = arr[top][i];
+                    arr[top][i] = 0;
+                    index++;
+                }
+            }
+            top++;
+            for (int i = 0; i < arr.length; i++) {
+                if (isValid(arr, i, right)) {
+                    result[index] = arr[i][right];
+                    arr[i][right] = 0;
+                    index++;
+                }
+            }
+            right--;
+            for (int i = arr[0].length - 1; i >= 0; i--) {
+                if (isValid(arr, down, i)) {
+                    result[index] = arr[down][i];
+                    arr[down][i] = 0;
+                    index++;
+                }
+            }
+            down--;
+            for (int i = arr.length - 1; i >= 0; i--) {
+                if (isValid(arr, i, left)) {
+                    result[index] = arr[i][left];
+                    arr[i][left] = 0;
+                    index++;
+                }
+            }
+            left++;
+        }
+        return result;
+    }
+
+    private boolean isValid(int[][] arr, int row, int col) {
+        return (row >= 0) &&
+                (row < arr.length) &&
+                (col >= 0) &&
+                (col < arr[0].length) &&
+                arr[row][col] != 0;
+    }
+
+}
\ No newline at end of file