Cleanup Saddleback Search

src/searching/saddleback_search.rs

@@ -1,85 +1,196 @@
-// Saddleback search is a technique used to find an element in a sorted 2D matrix in O(m + n) time,
-// where m is the number of rows, and n is the number of columns. It works by starting from the
-// top-right corner of the matrix and moving left or down based on the comparison of the current
-// element with the target element.
 use std::cmp::Ordering;
 
-pub fn saddleback_search(matrix: &[Vec<i32>], element: i32) -> (usize, usize) {
-    // Initialize left and right indices
+/// Custom error type to represent errors related to matrix validation.
+#[derive(Debug, PartialEq, Eq)]
+pub enum MatrixError {
+    NonRectangularMatrix,
+}
+
+/// Performs Saddleback search on a sorted 2D matrix.
+///
+/// The Saddleback search algorithm finds the position of a target element in a matrix where
+/// each row and each column is sorted in ascending order. The search starts from the top-right
+/// corner of the matrix and moves left or down based on comparisons with the target element.
+///
+/// # Arguments
+///
+/// * `matrix` - A 2D vector representing the sorted matrix.
+/// * `element` - The target element to search for.
+///
+/// # Returns
+///
+/// Returns `Ok(Some((row, column)))` where both indices are 0-based if the element is found.
+/// Returns `Ok(None)` if the element is not found.
+/// Returns `Err(MatrixError)` if the matrix is not rectangular.
+pub fn saddleback_search(
+    matrix: &[Vec<isize>],
+    element: isize,
+) -> Result<Option<(usize, usize)>, MatrixError> {
+    if matrix.is_empty() || matrix.iter().all(|row| row.is_empty()) {
+        return Ok(None);
+    }
+
+    if matrix.iter().any(|row| row.len() != matrix[0].len()) {
+        return Err(MatrixError::NonRectangularMatrix);
+    }
+
     let mut left_index = 0;
     let mut right_index = matrix[0].len() - 1;
 
-    // Start searching
     while left_index < matrix.len() {
         match element.cmp(&matrix[left_index][right_index]) {
-            // If the current element matches the target element, return its position (indices are 1-based)
-            Ordering::Equal => return (left_index + 1, right_index + 1),
+            Ordering::Equal => return Ok(Some((left_index, right_index))),
             Ordering::Greater => {
-                // If the target element is greater, move to the next row (downwards)
                 left_index += 1;
             }
             Ordering::Less => {
-                // If the target element is smaller, move to the previous column (leftwards)
                 if right_index == 0 {
-                    break; // If we reach the left-most column, exit the loop
+                    break;
                 } else {
                     right_index -= 1;
                 }
             }
         }
     }
 
-    // If the element is not found, return (0, 0)
-    (0, 0)
+    Ok(None)
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
-    // Test when the element is not present in the matrix
-    #[test]
-    fn test_element_not_found() {
-        let matrix = vec![vec![1, 10, 100], vec![2, 20, 200], vec![3, 30, 300]];
-        assert_eq!(saddleback_search(&matrix, 123), (0, 0));
-    }
-
-    // Test when the element is at the top-left corner of the matrix
-    #[test]
-    fn test_element_at_top_left() {
-        let matrix = vec![vec![1, 10, 100], vec![2, 20, 200], vec![3, 30, 300]];
-        assert_eq!(saddleback_search(&matrix, 1), (1, 1));
-    }
-
-    // Test when the element is at the bottom-right corner of the matrix
-    #[test]
-    fn test_element_at_bottom_right() {
-        let matrix = vec![vec![1, 10, 100], vec![2, 20, 200], vec![3, 30, 300]];
-        assert_eq!(saddleback_search(&matrix, 300), (3, 3));
-    }
-
-    // Test when the element is at the top-right corner of the matrix
-    #[test]
-    fn test_element_at_top_right() {
-        let matrix = vec![vec![1, 10, 100], vec![2, 20, 200], vec![3, 30, 300]];
-        assert_eq!(saddleback_search(&matrix, 100), (1, 3));
-    }
-
-    // Test when the element is at the bottom-left corner of the matrix
-    #[test]
-    fn test_element_at_bottom_left() {
-        let matrix = vec![vec![1, 10, 100], vec![2, 20, 200], vec![3, 30, 300]];
-        assert_eq!(saddleback_search(&matrix, 3), (3, 1));
+    macro_rules! saddleback_tests {
+        ($($name:ident: $tc:expr,)*) => {
+            $(
+                #[test]
+                fn $name() {
+                    let (matrix, element, expected) = $tc;
+                    assert_eq!(saddleback_search(&matrix, element), expected);
+                }
+            )*
+        };
     }
 
-    // Additional test case: Element in the middle of the matrix
-    #[test]
-    fn test_element_in_middle() {
-        let matrix = vec![
-            vec![1, 10, 100, 1000],
-            vec![2, 20, 200, 2000],
-            vec![3, 30, 300, 3000],
-        ];
-        assert_eq!(saddleback_search(&matrix, 200), (2, 3));
+    saddleback_tests! {
+        test_element_not_found: (
+            vec![
+                vec![1, 10, 100],
+                vec![2, 20, 200],
+                vec![3, 30, 300]
+            ],
+            123,
+            Ok(None::<(usize, usize)>),
+        ),
+        test_element_at_top_left: (
+            vec![
+                vec![1, 10, 100],
+                vec![2, 20, 200],
+                vec![3, 30, 300]
+            ],
+            1,
+            Ok(Some((0, 0))),
+        ),
+        test_element_at_bottom_right: (
+            vec![
+                vec![1, 10, 100],
+                vec![2, 20, 200],
+                vec![3, 30, 300]
+            ],
+            300,
+            Ok(Some((2, 2))),
+        ),
+        test_element_at_top_right: (
+            vec![
+                vec![1, 10, 100],
+                vec![2, 20, 200],
+                vec![3, 30, 300]
+            ],
+            100,
+            Ok(Some((0, 2))),
+        ),
+        test_element_at_bottom_left: (
+            vec![
+                vec![1, 10, 100],
+                vec![2, 20, 200],
+                vec![3, 30, 300]
+            ],
+            3,
+            Ok(Some((2, 0))),
+        ),
+        test_element_in_middle: (
+            vec![
+                vec![1, 10, 100, 1000],
+                vec![2, 20, 200, 2000],
+                vec![3, 30, 300, 3000],
+            ],
+            200,
+            Ok(Some((1, 2))),
+        ),
+        test_element_smaller_than_min: (
+            vec![
+                vec![1, 10, 100],
+                vec![2, 20, 200],
+                vec![3, 30, 300],
+            ],
+            0,
+            Ok(None::<(usize, usize)>),
+        ),
+        test_horizontal: (
+            vec![
+                vec![1, 10, 100],
+            ],
+            100,
+            Ok(Some((0, 2))),
+        ),
+        test_vertical: (
+            vec![
+                vec![1],
+                vec![2],
+                vec![3],
+            ],
+            2,
+            Ok(Some((1, 0))),
+        ),
+        test_single_element: (
+            vec![
+                vec![1],
+            ],
+            1,
+            Ok(Some((0, 0))),
+        ),
+        test_empty_matrix: (
+            vec![],
+            1,
+            Ok(None::<(usize, usize)>),
+        ),
+        test_non_rectangular_matrix: (
+            vec![
+                vec![1, 10, 100],
+                vec![2, 20],
+                vec![3, 30, 300],
+            ],
+            20,
+            Err::<Option<(usize, usize)>, MatrixError>(MatrixError::NonRectangularMatrix),
+        ),
+        test_empty_row: (
+            vec![
+                vec![1, 2, 3],
+                vec![],
+                vec![4, 5, 6],
+            ],
+            3,
+            Err::<Option<(usize, usize)>, MatrixError>(MatrixError::NonRectangularMatrix),
+        ),
+        test_full_empty_rows: (
+            vec![
+                vec![],
+                vec![],
+                vec![],
+                vec![],
+            ],
+            1,
+            Ok(None::<(usize, usize)>),
+        ),
     }
 }