From 4f35f764543adc898c4b509c86f0f05a77808337 Mon Sep 17 00:00:00 2001
From: Mariano Riefolo <rfmariano@protonmail.com>
Date: Wed, 21 Aug 2024 22:02:19 +0200
Subject: [PATCH] Wrote program for Day 27

---
 README.md                                     |  2 +-
 .../Day-27_Task-Scheduler/day27/Cargo.toml    |  6 ++++
 .../Day-27_Task-Scheduler/day27/src/lib.rs    | 35 +++++++++++++++++++
 .../Day-27_Task-Scheduler/day27/src/main.rs   | 33 +++++++++++++++++
 .../day27/tests/examples.rs                   | 25 +++++++++++++
 5 files changed, 100 insertions(+), 1 deletion(-)
 create mode 100644 Week-04/Day-27_Task-Scheduler/day27/Cargo.toml
 create mode 100644 Week-04/Day-27_Task-Scheduler/day27/src/lib.rs
 create mode 100644 Week-04/Day-27_Task-Scheduler/day27/src/main.rs
 create mode 100644 Week-04/Day-27_Task-Scheduler/day27/tests/examples.rs

diff --git a/README.md b/README.md
index 3981ebf..e0f899b 100644
--- a/README.md
+++ b/README.md
@@ -73,7 +73,7 @@ We encourage you to share your progress and ask questions in the Discussions sec
 | Day #24       | [The Josephus Problem](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-04/Day-24_The-Josephus-Problem)                  | :white_check_mark:      |
 | Day #25       | [Coin Trouble](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-04/Day-25_Coin-Trouble)                          | :white_check_mark:      |
 | Day #26       | [Briefcase Lock](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-04/Day-26_Briefcase-Lock)                        | :white_check_mark:      |
-| Day #27       | [Task Scheduler](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-04/Day-27_Task-Scheduler)                        | :white_large_square:      |
+| 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_large_square:      |
 | Day #29       | [Traffic Light Checker](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-05/Day-29_Traffic-Light-Checker)                 | :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_large_square:      |
diff --git a/Week-04/Day-27_Task-Scheduler/day27/Cargo.toml b/Week-04/Day-27_Task-Scheduler/day27/Cargo.toml
new file mode 100644
index 0000000..71d364d
--- /dev/null
+++ b/Week-04/Day-27_Task-Scheduler/day27/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "day27"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/Week-04/Day-27_Task-Scheduler/day27/src/lib.rs b/Week-04/Day-27_Task-Scheduler/day27/src/lib.rs
new file mode 100644
index 0000000..3e3cc3d
--- /dev/null
+++ b/Week-04/Day-27_Task-Scheduler/day27/src/lib.rs
@@ -0,0 +1,35 @@
+use std::collections::HashMap;
+
+pub fn task_scheduler(tasks: &[char], coldown: u8) -> u16 {
+    let mut num_tasks = HashMap::new();
+    for task in tasks {
+        *num_tasks.entry(task).or_insert(0) += 1;
+    }
+
+    let mut num_tasks: Vec<(&&char, &i32)> = num_tasks.iter().collect();
+    num_tasks.sort_by(|a, b| b.1.cmp(a.1));
+
+    let mut result = 0;
+    let mut pos = 0;
+    let mut range = 1;
+
+    for _ in 0..tasks.len() {
+        if num_tasks.get(pos as usize).is_none() {
+            result += if pos > coldown as u16 {
+                0
+            } else {
+                coldown as u16 - pos + 1
+            };
+            pos = 0;
+            range += 1;
+        }
+        if *num_tasks.get(pos as usize).unwrap().1 < range {
+            result += coldown as u16 - pos;
+            pos = 0;
+            range += 1;
+        }
+        result += 1;
+        pos += 1;
+    }
+    result
+}
diff --git a/Week-04/Day-27_Task-Scheduler/day27/src/main.rs b/Week-04/Day-27_Task-Scheduler/day27/src/main.rs
new file mode 100644
index 0000000..ac64a3d
--- /dev/null
+++ b/Week-04/Day-27_Task-Scheduler/day27/src/main.rs
@@ -0,0 +1,33 @@
+use std::io::{self, Write};
+
+use day27::task_scheduler;
+
+fn main() {
+    let mut buffer = String::new();
+
+    print!("Insert the task as a unique string: ");
+    io::stdout().flush().expect("Failed to flush");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read line");
+
+    let tasks: Vec<char> = buffer.trim().chars().collect();
+
+    buffer = String::new();
+
+    print!("Insert the length of the coldown: ");
+    io::stdout().flush().expect("Failed to flush");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read line");
+
+    let coldown = buffer
+        .trim()
+        .parse()
+        .expect("Coldown must be a valid unsigned integer");
+
+    let result = task_scheduler(&tasks, coldown);
+    println!("The least number of units of times that the CPU will take to finish all the given tasks is {}", result);
+}
diff --git a/Week-04/Day-27_Task-Scheduler/day27/tests/examples.rs b/Week-04/Day-27_Task-Scheduler/day27/tests/examples.rs
new file mode 100644
index 0000000..6698f68
--- /dev/null
+++ b/Week-04/Day-27_Task-Scheduler/day27/tests/examples.rs
@@ -0,0 +1,25 @@
+#[cfg(test)]
+mod examples {
+    use day27::task_scheduler;
+
+    #[test]
+    fn example1() {
+        assert_eq!(task_scheduler(&['A', 'A', 'A', 'B', 'B', 'B'], 2), 8);
+    }
+
+    #[test]
+    fn example2() {
+        assert_eq!(task_scheduler(&['A', 'A', 'A', 'B', 'B', 'B'], 0), 6);
+    }
+
+    #[test]
+    fn example3() {
+        assert_eq!(
+            task_scheduler(
+                &['A', 'A', 'A', 'A', 'A', 'A', 'B', 'C', 'D', 'E', 'F', 'G'],
+                2
+            ),
+            16
+        );
+    }
+}