Wrote program for Day 30

README.md

@@ -76,7 +76,7 @@ We encourage you to share your progress and ask questions in the Discussions sec
 | Day #27       | [Task Scheduler](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-04/Day-27_Task-Scheduler)                        | :white_check_mark:      |
 | Day #28       | [Word Search](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-04/Day-28_Word-Search)                           | :white_check_mark:      |
 | Day #29       | [Traffic Light Checker](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-05/Day-29_Traffic-Light-Checker)                 | :white_check_mark:      |
-| Day #30       | [The Maximum Value](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-05/Day-30_The-Maximum-Value)                     | :white_large_square:      |
+| Day #30       | [The Maximum Value](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-05/Day-30_The-Maximum-Value)                     | :white_check_mark:      |
 | Day #31       | [The Time In Words](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-05/Day-31_The-Time-In-Words)                     | :white_large_square:      |
 | Day #32       | [Climbing The Leaderboard](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-05/Day-32_Climbing-The-Leaderboard)              | :white_large_square:      |
 | Day #33       | [WERTYU](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-05/Day-33_WERTYU)                                | :white_large_square:      |

Week-05/Day-30_The-Maximum-Value/day30/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day30"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

Week-05/Day-30_The-Maximum-Value/day30/src/lib.rs

@@ -0,0 +1,27 @@
+pub fn max_value(mut n: isize, digit: char) -> Result<isize, String> {
+    let digit = match digit.to_digit(10) {
+        Some(d) => Ok(d as isize),
+        None => Err("The digit is not valid"),
+    }?;
+
+    let negative = n < 0;
+    if negative {
+        n *= -1;
+    }
+
+    let nlen = (n.abs() as f32).log10().floor() as u32 + 1;
+    let mut max = n * 10 + digit;
+
+    let cmp = if negative {
+        std::cmp::min
+    } else {
+        std::cmp::max
+    };
+
+    for i in 1..=nlen {
+        let option = (n / 10isize.pow(i) * 10 + digit) * 10isize.pow(i) + n % 10isize.pow(i);
+        max = cmp(max, option);
+    }
+
+    Ok(if negative { -max } else { max })
+}

Week-05/Day-30_The-Maximum-Value/day30/src/main.rs

@@ -0,0 +1,46 @@
+use std::io::{self, Write};
+use std::process::exit;
+
+use day30::max_value;
+
+fn main() {
+    let mut buffer = String::new();
+
+    print!("Insert the starting number: ");
+    io::stdout().flush().expect("Failed to flush stdout");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read line");
+
+    let n: isize = match buffer.trim().parse() {
+        Ok(n) => n,
+        Err(_) => {
+            eprintln!("Invalid number");
+            exit(1);
+        }
+    };
+
+    buffer.clear();
+
+    print!("Insert the digit to add to the number: ");
+    io::stdout().flush().expect("Failed to flush stdout");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read line");
+
+    let digit: char = match buffer.trim().parse() {
+        Ok(digit) => digit,
+        Err(_) => {
+            eprintln!("Invalid digit");
+            exit(1);
+        }
+    };
+
+    let result = max_value(n, digit);
+    match result {
+        Ok(result) => println!("The maximum value possible is: {}", result),
+        Err(e) => eprintln!("Error: {}", e),
+    }
+}

Week-05/Day-30_The-Maximum-Value/day30/tests/examples.rs

@@ -0,0 +1,24 @@
+#[cfg(test)]
+mod examples {
+    use day30::max_value;
+
+    #[test]
+    fn example1() {
+        assert_eq!(max_value(276, '3'), Ok(3276));
+    }
+
+    #[test]
+    fn example2() {
+        assert_eq!(max_value(-999, '4'), Ok(-4999));
+    }
+
+    #[test]
+    fn example3() {
+        assert_eq!(max_value(0, '3'), Ok(30));
+    }
+
+    #[test]
+    fn example4() {
+        assert_eq!(max_value(860, '7'), Ok(8760));
+    }
+}