Refator Egg Dropping Implementation (#776)

* ref: improve egg dropping implementation

* chore: update docstring

* style: use proper grammar

---------

Co-authored-by: Piotr Idzik <[email protected]>

Author: sozelfist

src/dynamic_programming/egg_dropping.rs

@@ -1,91 +1,84 @@
-/// # Egg Dropping Puzzle
+//! This module contains the `egg_drop` function, which determines the minimum number of egg droppings
+//! required to find the highest floor from which an egg can be dropped without breaking. It also includes
+//! tests for the function using various test cases, including edge cases.
 
-/// `egg_drop(eggs, floors)` returns the least number of egg droppings
-///     required to determine the highest floor from which an egg will not
-///     break upon dropping
+/// Returns the least number of egg droppings required to determine the highest floor from which an egg will not break upon dropping.
 ///
-/// Assumptions: n > 0
-pub fn egg_drop(eggs: u32, floors: u32) -> u32 {
-    assert!(eggs > 0);
-
-    // Explicity handle edge cases (optional)
-    if eggs == 1 || floors == 0 || floors == 1 {
-        return floors;
-    }
-
-    let eggs_index = eggs as usize;
-    let floors_index = floors as usize;
-
-    // Store solutions to subproblems in 2D Vec,
-    // where egg_drops[i][j] represents the solution to the egg dropping
-    // problem with i eggs and j floors
-    let mut egg_drops: Vec<Vec<u32>> = vec![vec![0; floors_index + 1]; eggs_index + 1];
-
-    // Assign solutions for egg_drop(n, 0) = 0, egg_drop(n, 1) = 1
-    for egg_drop in egg_drops.iter_mut().skip(1) {
-        egg_drop[0] = 0;
-        egg_drop[1] = 1;
-    }
-
-    // Assign solutions to egg_drop(1, k) = k
-    for j in 1..=floors_index {
-        egg_drops[1][j] = j as u32;
+/// # Arguments
+///
+/// * `eggs` - The number of eggs available.
+/// * `floors` - The number of floors in the building.
+///
+/// # Returns
+///
+/// * `Some(usize)` - The minimum number of drops required if the number of eggs is greater than 0.
+/// * `None` - If the number of eggs is 0.
+pub fn egg_drop(eggs: usize, floors: usize) -> Option<usize> {
+    if eggs == 0 {
+        return None;
     }
 
-    // Complete solutions vector using optimal substructure property
-    for i in 2..=eggs_index {
-        for j in 2..=floors_index {
-            egg_drops[i][j] = u32::MAX;
-
-            for k in 1..=j {
-                let res = 1 + std::cmp::max(egg_drops[i - 1][k - 1], egg_drops[i][j - k]);
-
-                if res < egg_drops[i][j] {
-                    egg_drops[i][j] = res;
-                }
-            }
-        }
+    if eggs == 1 || floors == 0 || floors == 1 {
+        return Some(floors);
     }
 
-    egg_drops[eggs_index][floors_index]
+    // Create a 2D vector to store solutions to subproblems
+    let mut egg_drops: Vec<Vec<usize>> = vec![vec![0; floors + 1]; eggs + 1];
+
+    // Base cases: 0 floors -> 0 drops, 1 floor -> 1 drop
+    (1..=eggs).for_each(|i| {
+        egg_drops[i][1] = 1;
+    });
+
+    // Base case: 1 egg -> k drops for k floors
+    (1..=floors).for_each(|j| {
+        egg_drops[1][j] = j;
+    });
+
+    // Fill the table using the optimal substructure property
+    (2..=eggs).for_each(|i| {
+        (2..=floors).for_each(|j| {
+            egg_drops[i][j] = (1..=j)
+                .map(|k| 1 + std::cmp::max(egg_drops[i - 1][k - 1], egg_drops[i][j - k]))
+                .min()
+                .unwrap();
+        });
+    });
+
+    Some(egg_drops[eggs][floors])
 }
 
 #[cfg(test)]
 mod tests {
-    use super::egg_drop;
-
-    #[test]
-    fn zero_floors() {
-        assert_eq!(egg_drop(5, 0), 0);
-    }
-
-    #[test]
-    fn one_egg() {
-        assert_eq!(egg_drop(1, 8), 8);
-    }
-
-    #[test]
-    fn eggs2_floors2() {
-        assert_eq!(egg_drop(2, 2), 2);
-    }
-
-    #[test]
-    fn eggs3_floors5() {
-        assert_eq!(egg_drop(3, 5), 3);
-    }
-
-    #[test]
-    fn eggs2_floors10() {
-        assert_eq!(egg_drop(2, 10), 4);
-    }
-
-    #[test]
-    fn eggs2_floors36() {
-        assert_eq!(egg_drop(2, 36), 8);
+    use super::*;
+
+    macro_rules! egg_drop_tests {
+        ($($name:ident: $test_cases:expr,)*) => {
+            $(
+                #[test]
+                fn $name() {
+                    let (eggs, floors, expected) = $test_cases;
+                    assert_eq!(egg_drop(eggs, floors), expected);
+                }
+            )*
+        }
     }
 
-    #[test]
-    fn large_floors() {
-        assert_eq!(egg_drop(2, 100), 14);
+    egg_drop_tests! {
+        test_no_floors: (5, 0, Some(0)),
+        test_one_egg_multiple_floors: (1, 8, Some(8)),
+        test_multiple_eggs_one_floor: (5, 1, Some(1)),
+        test_two_eggs_two_floors: (2, 2, Some(2)),
+        test_three_eggs_five_floors: (3, 5, Some(3)),
+        test_two_eggs_ten_floors: (2, 10, Some(4)),
+        test_two_eggs_thirty_six_floors: (2, 36, Some(8)),
+        test_many_eggs_one_floor: (100, 1, Some(1)),
+        test_many_eggs_few_floors: (100, 5, Some(3)),
+        test_few_eggs_many_floors: (2, 1000, Some(45)),
+        test_zero_eggs: (0, 10, None::<usize>),
+        test_no_eggs_no_floors: (0, 0, None::<usize>),
+        test_one_egg_no_floors: (1, 0, Some(0)),
+        test_one_egg_one_floor: (1, 1, Some(1)),
+        test_maximum_floors_one_egg: (1, usize::MAX, Some(usize::MAX)),
     }
 }