[LeetCode Sync] Runtime - 4 ms (39.49%), Memory - 9 MB (57.83%)

Author: NamVr

0048-rotate-image/README.md

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+<p>You are given an <code>n x n</code> 2D <code>matrix</code> representing an image, rotate the image by <strong>90</strong> degrees (clockwise).</p>
+
+<p>You have to rotate the image <a href="https://en.wikipedia.org/wiki/In-place_algorithm" target="_blank"><strong>in-place</strong></a>, which means you have to modify the input 2D matrix directly. <strong>DO NOT</strong> allocate another 2D matrix and do the rotation.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/08/28/mat1.jpg" style="width: 500px; height: 188px;" />
+<pre>
+<strong>Input:</strong> matrix = [[1,2,3],[4,5,6],[7,8,9]]
+<strong>Output:</strong> [[7,4,1],[8,5,2],[9,6,3]]
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/08/28/mat2.jpg" style="width: 500px; height: 201px;" />
+<pre>
+<strong>Input:</strong> matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
+<strong>Output:</strong> [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>n == matrix.length == matrix[i].length</code></li>
+	<li><code>1 &lt;= n &lt;= 20</code></li>
+	<li><code>-1000 &lt;= matrix[i][j] &lt;= 1000</code></li>
+</ul>

0048-rotate-image/solution.cpp

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+class Solution {
+public:
+    void rotate(vector<vector<int>>& matrix) {
+        int l = 0, r = matrix.size()-1;
+
+        while (l < r) {
+            for (int i = 0; i < r-l; i++) {
+                int t = l, b = r;
+
+                int temp = matrix[t][l+i];
+                matrix[t][l+i] = matrix[b-i][l]; 
+                matrix[b-i][l] = matrix[b][r-i];
+                matrix[b][r-i] = matrix[t+i][r];
+                matrix[t+i][r] = temp;
+            }
+            l++;
+            r--;
+        }
+    }
+};