1 files changed, 57 insertions, 0 deletions
diff --git a/src/lib/sudoku/validation.ts b/src/lib/sudoku/validation.ts
new file mode 100644
index 0000000..4403a20
--- /dev/null
+++ b/src/lib/sudoku/validation.ts
@@ -0,0 +1,57 @@
+import type { Coord, Grid } from "../Sudoku";
+
+export function validate(board: Grid) {
+  const bads = [] as Coord[];
+  for (let i = 0; i < 9; i++) {
+    for (let j = 0; j < 9; j++) {
+      const value = board[i][j];
+      if (value !== '.') {
+        if (!validateRow(board, i, j, value) || !validateColumn(board, i, j, value) || !validateBox(board, i, j, value)) {
+          bads.push({ x: i, y: j })
+        }
+      }
+    }
+  }
+  return bads;
+};
+
+function validateRow(board: Grid, row: number, col: number, value: string) {
+  for (let j = 0; j < 9; j++) {
+    if (j !== col) {
+      if (board[row][j] === value) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+function validateColumn(board: Grid, row: number, col: number, value: string) {
+  for (let i = 0; i < 9; i++) {
+    if (i !== row) {
+      if (board[i][col] === value) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+function validateBox(board: Grid, row: number, col: number, value: string) {
+  const startRow = row - (row % 3), startCol = col - (col % 3);
+
+  for (let i = startRow; i < startRow + 3; i++) {
+    for (let j = startCol; j < startCol + 3; j++) {
+      if (i !== row && j !== col) {
+        if (board[i][j] === value) {
+          return false;
+        }
+      }
+    }
+  }
+
+  return true;
+}
+