Wrote program for Day 18

README.md

@@ -64,7 +64,7 @@ We encourage you to share your progress and ask questions in the Discussions sec
 | Day #15       | [Valid Anagram](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-15_Valid-Anagram)                         | :white_check_mark:      |
 | Day #16       | [Nim Game](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-16_Nim-Game)                              | :white_check_mark:      |
 | Day #17       | [Prison Break](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-17_Prison-Break)                          | :white_check_mark:      |
-| Day #18       | [Unique Paths](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-18_Unique-Paths)                          | :white_large_square:      |
+| Day #18       | [Unique Paths](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-18_Unique-Paths)                          | :white_check_mark:      |
 | Day #19       | [URL Shortener](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-19_URL-Shortener)                         | :white_large_square:      |
 | Day #20       | [API Challenge](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-20_API-Challenge)                         | :white_large_square:      |
 | Day #21       | [Random Maze Generator](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-21_Random-Maze-Generator)                 | :white_large_square:      |

Week-03/Day-18_Unique-Paths/day18/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day18"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

Week-03/Day-18_Unique-Paths/day18/src/lib.rs

@@ -0,0 +1,28 @@
+use std::collections::HashMap;
+
+pub fn unique_paths(m: u8, n: u8) -> u16 {
+    let mut memo: HashMap<u8, HashMap<u8, u16>> = HashMap::new();
+    memo.entry(1).or_default().insert(1, 1);
+    count_unique_paths(m, n, &mut memo)
+}
+
+fn count_unique_paths(m: u8, n: u8, memo: &mut HashMap<u8, HashMap<u8, u16>>) -> u16 {
+    let memo_m = memo.get(&m);
+    let memo_n = memo_m.and_then(|m_m| m_m.get(&n));
+
+    if let Some(&result) = memo_n {
+        result
+    } else if m == 1 {
+        let result = unique_paths(m, n - 1);
+        memo.entry(m).or_default().insert(n, result);
+        result
+    } else if n == 1 {
+        let result = unique_paths(m - 1, n);
+        memo.entry(m).or_default().insert(n, result);
+        result
+    } else {
+        let result = unique_paths(m, n - 1) + unique_paths(m - 1, n);
+        memo.entry(m).or_default().insert(n, result);
+        result
+    }
+}

Week-03/Day-18_Unique-Paths/day18/src/main.rs

@@ -0,0 +1,27 @@
+use std::io::{self, Write};
+
+use day18::unique_paths;
+
+fn get_number(request: &str) -> u8 {
+    let mut buffer = String::new();
+
+    print!("{}", request);
+    io::stdout().flush().expect("Failed to flush stout");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read from stdin");
+
+    buffer.trim().parse().expect("The input is not a number")
+}
+
+fn main() {
+    let m = get_number("Insert the height: ");
+    let n = get_number("Insert the width: ");
+    let result = unique_paths(m, n);
+
+    println!(
+        "There are {} unique paths from ({}, {}) to (1, 1)",
+        result, m, n
+    );
+}

Week-03/Day-18_Unique-Paths/day18/tests/examples.rs

@@ -0,0 +1,24 @@
+#[cfg(test)]
+mod examples {
+    use day18::unique_paths;
+
+    #[test]
+    fn example1() {
+        assert_eq!(unique_paths(3, 7), 28);
+    }
+
+    #[test]
+    fn example2() {
+        assert_eq!(unique_paths(3, 2), 3);
+    }
+
+    #[test]
+    fn example3() {
+        assert_eq!(unique_paths(7, 3), 28);
+    }
+
+    #[test]
+    fn example4() {
+        assert_eq!(unique_paths(3, 3), 6);
+    }
+}