Solve Problem 840. Magic Squares In Grid

README.md

@@ -150,6 +150,7 @@ LeetSpace serves as a dedicated workspace and archive for my [LeetCode](https://
 | [823. Binary Trees With Factors](https://leetcode.com/problems/binary-trees-with-factors) | Medium | [C++](./problems/0823/solution.cpp) |
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 | [834. Sum of Distances in Tree](https://leetcode.com/problems/sum-of-distances-in-tree/) | Hard | [C](./old-problems/0834/c/solution.c) [C++](./old-problems/0834/solution.cpp) |
+| [840. Magic Squares In Grid](https://leetcode.com/problems/magic-squares-in-grid/) | Medium | [C++](./old-problems/0840/solution.cpp) |
 | [844. Backspace String Compare](https://leetcode.com/problems/backspace-string-compare) | Easy | [C++](./problems/0844/solution.cpp) |
 | [846. Hand of Straights](https://leetcode.com/problems/hand-of-straights/) | medium | [C](./old-problems/0846/c/solution.c) [C++](./old-problems/0846/solution.cpp) |
 | [857. Minimum Cost to Hire K Workers](https://leetcode.com/problems/minimum-cost-to-hire-k-workers/) | Hard | [C++](./old-problems/0857/solution.cpp) |

old-problems/0840/CMakeLists.txt

@@ -0,0 +1,2 @@
+get_dir_name(id)
+add_problem_test(test-${id} test.yaml)

old-problems/0840/solution.cpp

@@ -0,0 +1,79 @@
+#include <vector>
+
+class Solution {
+ public:
+  int numMagicSquaresInside(std::vector<std::vector<int>>& grid) {
+    int num{0};
+    for (int i = grid.size() - 2; i > 0; --i) {
+      for (int j = grid[i].size() - 2; j > 0; --j) {
+        if (grid[i][j] != 5) continue;
+        switch (grid[i - 1][j - 1]) {
+          case 2:
+            switch (grid[i - 1][j]) {
+              case 9:
+                if (grid[i - 1][j + 1] == 4 && grid[i][j - 1] == 7 &&
+                    grid[i][j + 1] == 3 && grid[i + 1][j - 1] == 6 &&
+                    grid[i + 1][j] == 1 && grid[i + 1][j + 1] == 8) ++num;
+                break;
+
+              case 7:
+                if (grid[i - 1][j + 1] == 6 && grid[i][j - 1] == 9 &&
+                    grid[i][j + 1] == 1 && grid[i + 1][j - 1] == 4 &&
+                    grid[i + 1][j] == 3 && grid[i + 1][j + 1] == 8) ++num;
+                break;
+            }
+            break;
+
+          case 4:
+            switch (grid[i - 1][j]) {
+              case 3:
+                if (grid[i - 1][j + 1] == 8 && grid[i][j - 1] == 9 &&
+                    grid[i][j + 1] == 1 && grid[i + 1][j - 1] == 2 &&
+                    grid[i + 1][j] == 7 && grid[i + 1][j + 1] == 6) ++num;
+                break;
+
+              case 9:
+                if (grid[i - 1][j + 1] == 2 && grid[i][j - 1] == 3 &&
+                    grid[i][j + 1] == 7 && grid[i + 1][j - 1] == 8 &&
+                    grid[i + 1][j] == 1 && grid[i + 1][j + 1] == 6) ++num;
+                break;
+            }
+            break;
+
+          case 6:
+            switch (grid[i - 1][j]) {
+              case 7:
+                if (grid[i - 1][j + 1] == 2 && grid[i][j - 1] == 1 &&
+                    grid[i][j + 1] == 9 && grid[i + 1][j - 1] == 8 &&
+                    grid[i + 1][j] == 3 && grid[i + 1][j + 1] == 4) ++num;
+                break;
+
+              case 1:
+                if (grid[i - 1][j + 1] == 8 && grid[i][j - 1] == 7 &&
+                    grid[i][j + 1] == 3 && grid[i + 1][j - 1] == 2 &&
+                    grid[i + 1][j] == 9 && grid[i + 1][j + 1] == 4) ++num;
+                break;
+            }
+            break;
+
+          case 8:
+            switch (grid[i - 1][j]) {
+              case 1:
+                if (grid[i - 1][j + 1] == 6 && grid[i][j - 1] == 3 &&
+                    grid[i][j + 1] == 7 && grid[i + 1][j - 1] == 4 &&
+                    grid[i + 1][j] == 9 && grid[i + 1][j + 1] == 2) ++num;
+                break;
+
+              case 3:
+                if (grid[i - 1][j + 1] == 4 && grid[i][j - 1] == 1 &&
+                    grid[i][j + 1] == 9 && grid[i + 1][j - 1] == 6 &&
+                    grid[i + 1][j] == 7 && grid[i + 1][j + 1] == 2) ++num;
+                break;
+            }
+            break;
+        }
+      }
+    }
+    return num;
+  }
+};

old-problems/0840/test.yaml

@@ -0,0 +1,32 @@
+name: 840. Magic Squares In Grid
+
+types:
+  inputs:
+    grid: std::vector<std::vector<int>>
+  output: int
+
+solutions:
+  cpp:
+    function: numMagicSquaresInside
+
+test_cases:
+  example_1:
+    inputs:
+      grid:
+        - [4, 3, 8, 4]
+        - [9, 5, 1, 9]
+        - [2, 7, 6, 2]
+    output: 1
+
+  example_2:
+    inputs:
+      grid: [[8]]
+    output: 0
+
+  test_case_8:
+    inputs:
+      grid:
+        - [4, 7, 8]
+        - [9, 5, 1]
+        - [2, 3, 6]
+    output: 0