Added Valid Sudoku

Author: ryanoneill

src/valid_sudoku.rs

@@ -1,26 +1,135 @@
-/// TODO: Fill In
+/// Determine if a `9 x 9` Sudoku board is valid. Only the filled cells need to
+/// be validated according to the following rules:
+///
+/// Each row must contain the digits `1-9` without repetition.
+///
+/// Each column must contain the digits `1-9` without repetition.
+///
+/// Each of the nine `3 x 3` sub-boxes of the grid must contain the digits `1-9`
+/// without repetition.
+///
+/// Note:
+/// * A Sudoku board (partially filled) could be valid but is not necessarily
+///   solvable.
+///
+/// * Only the filled cells need to be validated according to the mentioned
+///   rules.
 struct Solution;
 
 impl Solution {
-    // TODO: Implement
-    pub fn is_valid_sudoku(_board: Vec<Vec<char>>) -> bool {
-        false
+
+    fn char_to_index(c: char) -> usize {
+        c.to_digit(10).unwrap_or_default() as usize
+    }
+
+    fn is_valid_component<F>(board: &Vec<Vec<char>>, f: F) -> bool
+        where F: Fn(&Vec<Vec<char>>, usize) -> char {
+
+        let mut result = true;
+        let mut working = vec![0; 10];
+        for i in 0..9 {
+            let value = f(board, i);
+            if value != '.' {
+                let w = Self::char_to_index(value);
+                if working[w] == w {
+                    result = false;
+                    break;
+                } else { working[w] = w; }
+            }
+        }
+
+        result
+    }
+
+    fn is_valid_section(board: &Vec<Vec<char>>, sec: usize) -> bool {
+        let row_offset = match sec {
+            0 | 1 | 2 => 0,
+            3 | 4 | 5 => 3,
+            6 | 7 | 8 => 6,
+            _ => 0,
+        };
+        let col_offset = match sec {
+            0 | 3 | 6 => 0,
+            1 | 4 | 7 => 3,
+            2 | 5 | 8 => 6,
+            _ => 0,
+        };
+
+        Self::is_valid_component(board, |board, num| {
+            let (row, col) = match num {
+                0 => (0 + row_offset, 0 + col_offset),
+                1 => (0 + row_offset, 1 + col_offset),
+                2 => (0 + row_offset, 2 + col_offset),
+                3 => (1 + row_offset, 0 + col_offset),
+                4 => (1 + row_offset, 1 + col_offset),
+                5 => (1 + row_offset, 2 + col_offset),
+                6 => (2 + row_offset, 0 + col_offset),
+                7 => (2 + row_offset, 1 + col_offset),
+                8 => (2 + row_offset, 2 + col_offset),
+                _ => (0, 0)
+            };
+            board[row][col]
+        })
+    }
+
+    fn is_valid_column(board: &Vec<Vec<char>>, col: usize) -> bool {
+        Self::is_valid_component(board, |board, row| board[row][col])
+    }
+
+    fn is_valid_row(board: &Vec<Vec<char>>, row: usize) -> bool {
+        Self::is_valid_component(board, |board, col| board[row][col])
     }
+
+    pub fn is_valid_sudoku(board: Vec<Vec<char>>) -> bool {
+        let mut result = true;
+
+        for i in 0..9 {
+            result = result && Self::is_valid_row(&board, i);
+            result = result && Self::is_valid_column(&board, i);
+            result = result && Self::is_valid_section(&board, i);
+        }
+
+        result
+    }
+
 }
 
 #[cfg(test)]
 mod tests {
     use super::Solution;
 
-    #[ignore]
     #[test]
     fn example_1() {
-        // TODO: Fill In
+        let board = vec![
+            vec!['5','3','.','.','7','.','.','.','.'],
+            vec!['6','.','.','1','9','5','.','.','.'],
+            vec!['.','9','8','.','.','.','.','6','.'],
+            vec!['8','.','.','.','6','.','.','.','3'],
+            vec!['4','.','.','8','.','3','.','.','1'],
+            vec!['7','.','.','.','2','.','.','.','6'],
+            vec!['.','6','.','.','.','.','2','8','.'],
+            vec!['.','.','.','4','1','9','.','.','5'],
+            vec!['.','.','.','.','8','.','.','7','9']
+        ];
+        let result = Solution::is_valid_sudoku(board);
+        assert!(result);
     }
 
-    #[ignore]
     #[test]
     fn example_2() {
-        // TODO: Fill In
+        let board = vec![
+            vec!['8','3','.','.','7','.','.','.','.'],
+            vec!['6','.','.','1','9','5','.','.','.'],
+            vec!['.','9','8','.','.','.','.','6','.'],
+            vec!['8','.','.','.','6','.','.','.','3'],
+            vec!['4','.','.','8','.','3','.','.','1'],
+            vec!['7','.','.','.','2','.','.','.','6'],
+            vec!['.','6','.','.','.','.','2','8','.'],
+            vec!['.','.','.','4','1','9','.','.','5'],
+            vec!['.','.','.','.','8','.','.','7','9']
+        ];
+        let result = Solution::is_valid_sudoku(board);
+        assert!(!result);
     }
+
 }