feat: add js solution to lc problem: No.0840

Author: rain84

solution/0800-0899/0840.Magic Squares In Grid/README.md

@@ -374,6 +374,52 @@ export function numMagicSquaresInside(grid: number[][]): number {
 }
 ```
 
+#### JavaScript
+
+```js
+function numMagicSquaresInside(grid) {
+    const [m, n] = [grid.length, grid[0].length];
+    if (m < 3 || n < 3) return 0;
+
+    const check = (y, x) => {
+        const g = grid;
+        if (g[y + 1][x + 1] !== 5) return false;
+
+        const cells = [
+            g[y][x],
+            g[y][x + 1],
+            g[y][x + 2],
+            g[y + 1][x + 2],
+            g[y + 2][x + 2],
+            g[y + 2][x + 1],
+            g[y + 2][x],
+            g[y + 1][x],
+        ];
+
+        const i = cells.indexOf(2);
+        if (i === -1) return false;
+        cells.push(...cells.splice(0, i));
+
+        const circle = [2, 9, 4, 3, 8, 1, 6, 7];
+        const reverseCircle = [2, 7, 6, 1, 8, 3, 4, 9];
+
+        if (cells.every((x, i) => x === circle[i])) return true;
+        if (cells.every((x, i) => x === reverseCircle[i])) return true;
+
+        return false;
+    };
+
+    let res = 0;
+    for (let i = 0; i < m - 2; i++) {
+        for (let j = 0; j < n - 2; j++) {
+            res += +check(i, j);
+        }
+    }
+
+    return res;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/0800-0899/0840.Magic Squares In Grid/README_EN.md

@@ -370,6 +370,52 @@ export function numMagicSquaresInside(grid: number[][]): number {
 }
 ```
 
+#### JavaScript
+
+```js
+function numMagicSquaresInside(grid) {
+    const [m, n] = [grid.length, grid[0].length];
+    if (m < 3 || n < 3) return 0;
+
+    const check = (y, x) => {
+        const g = grid;
+        if (g[y + 1][x + 1] !== 5) return false;
+
+        const cells = [
+            g[y][x],
+            g[y][x + 1],
+            g[y][x + 2],
+            g[y + 1][x + 2],
+            g[y + 2][x + 2],
+            g[y + 2][x + 1],
+            g[y + 2][x],
+            g[y + 1][x],
+        ];
+
+        const i = cells.indexOf(2);
+        if (i === -1) return false;
+        cells.push(...cells.splice(0, i));
+
+        const circle = [2, 9, 4, 3, 8, 1, 6, 7];
+        const reverseCircle = [2, 7, 6, 1, 8, 3, 4, 9];
+
+        if (cells.every((x, i) => x === circle[i])) return true;
+        if (cells.every((x, i) => x === reverseCircle[i])) return true;
+
+        return false;
+    };
+
+    let res = 0;
+    for (let i = 0; i < m - 2; i++) {
+        for (let j = 0; j < n - 2; j++) {
+            res += +check(i, j);
+        }
+    }
+
+    return res;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/0800-0899/0840.Magic Squares In Grid/Solution2.js

@@ -0,0 +1,41 @@
+function numMagicSquaresInside(grid) {
+    const [m, n] = [grid.length, grid[0].length];
+    if (m < 3 || n < 3) return 0;
+
+    const check = (y, x) => {
+        const g = grid;
+        if (g[y + 1][x + 1] !== 5) return false;
+
+        const cells = [
+            g[y][x],
+            g[y][x + 1],
+            g[y][x + 2],
+            g[y + 1][x + 2],
+            g[y + 2][x + 2],
+            g[y + 2][x + 1],
+            g[y + 2][x],
+            g[y + 1][x],
+        ];
+
+        const i = cells.indexOf(2);
+        if (i === -1) return false;
+        cells.push(...cells.splice(0, i));
+
+        const circle = [2, 9, 4, 3, 8, 1, 6, 7];
+        const reverseCircle = [2, 7, 6, 1, 8, 3, 4, 9];
+
+        if (cells.every((x, i) => x === circle[i])) return true;
+        if (cells.every((x, i) => x === reverseCircle[i])) return true;
+
+        return false;
+    };
+
+    let res = 0;
+    for (let i = 0; i < m - 2; i++) {
+        for (let j = 0; j < n - 2; j++) {
+            res += +check(i, j);
+        }
+    }
+
+    return res;
+}