fix: update descriptions

Author: tanhongit

medium/840. Magic Squares In Grid/description.md

@@ -0,0 +1,39 @@
+URL: [840. Magic Squares In Grid
+](https://leetcode.com/problems/magic-squares-in-grid/description/)
+
+A `3 x 3` magic square is a `3 x 3` grid filled with distinct numbers from 1 to 9 such that each row, column, and both diagonals all have the same sum.
+
+Given a `row x col` `grid` of integers, how many `3 x 3` contiguous magic square subgrids are there?
+
+Note: while a magic square can only contain numbers from 1 to 9, grid may contain numbers up to 15.
+
+![img.png](img.png)
+
+**Example 1:**
+
+
+- Input: `grid = [[4,3,8,4],[9,5,1,9],[2,7,6,2]]`
+- Output: 1
+- Explanation: The following subgrid is a `3 x 3` magic square:
+
+![img_1.png](img_1.png)
+
+while this one is not:
+
+![img_2.png](img_2.png)
+- 
+In total, there is only one magic square inside the given grid.
+
+**Example 2:**
+
+> Input: `grid = [[8]]`
+> 
+> Output: `0`
+
+
+**Constraints:**
+
+- `row == grid.length`
+- `col == grid[i].length`
+- `1 <= row, col <= 10`
+- `0 <= grid[i][j] <= 15`

medium/840. Magic Squares In Grid/img.png

@@ -11,19 +11,23 @@ Return an array of coordinates representing the positions of the grid in the ord
 
 Example 1:
 
+![img.png](img.png)
+
 > **Input:** rows = 1, cols = 4, rStart = 0, cStart = 0
 > 
 > **Output:** [[0,0],[0,1],[0,2],[0,3]]
 
 Example 2:
 
+![img_1.png](img_1.png)
+
 > **Input:** rows = 5, cols = 6, rStart = 1, cStart = 4
 > 
 > **Output:** [[1,4],[1,5],[2,5],[2,4],[2,3],[1,3],[0,3],[0,4],[0,5],[3,5],[3,4],[3,3],[3,2],[2,2],[1,2],[0,2],[4,5],[4,4],[4,3],[4,2],[4,1],[3,1],[2,1],[1,1],[0,1],[4,0],[3,0],[2,0],[1,0],[0,0]]
 
 
 Constraints:
 
-- 1 <= rows, cols <= 100
-- 0 <= rStart < rows
-- 0 <= cStart < cols
+- `1 <= rows, cols <= 100`
+- `0 <= rStart < rows`
+- `0 <= cStart < cols`