add code of 48

Author: Li Li

top-interview-questions/48. Rotate Image.cs

@@ -0,0 +1,24 @@
+// clock-wise rotate,先对角对折, 再横向对折
+// anti-clockwise, reverse the step, 横向对折 -> 对角对折,
+public class Solution {
+    public void Rotate(int[,] matrix) {
+        int m = matrix.GetLength(0);
+        int n = matrix.GetLength(1);
+        // 先对角对折
+        for (int i = 0; i < m; i++) {
+            for (int j = i; j < n; j++) {
+                int temp = matrix[i, j];
+                matrix[i, j] = matrix[j, i];
+                matrix[j, i] = temp;
+            }
+        }
+        // 再横向对折
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n / 2; j++) {
+                int temp = matrix[i, j];
+                matrix[i, j] = matrix[i, n - j - 1];
+                matrix[i, n - j - 1] = temp;
+            }
+        }
+    }
+}