feat: add solution for task scheduler in rust

Author: bujosa

src/medium/task_scheduler.rs

@@ -0,0 +1,70 @@
+#![allow(dead_code)]
+use std::collections::{BinaryHeap, VecDeque};
+
+fn least_interval(tasks: Vec<char>, n: usize) -> usize {
+    let mut heap = BinaryHeap::new();
+    let mut q = VecDeque::new();
+    let mut map = vec![0; 26];
+
+    for t in tasks {
+        map[(t as u8 - 'A' as u8) as usize] += 1;
+    }
+
+    for (i, cnt) in map.into_iter().enumerate() {
+        if cnt > 0 {
+            let c = ('A' as u8 + i as u8) as char;
+            heap.push((cnt, c));
+        }
+    }
+
+    let mut time = 0;
+
+    while !heap.is_empty() || !q.is_empty() {
+        while let Some(item) = q.pop_front() {
+            let (process_time, cnt, c) = item;
+
+            if process_time < time {
+                heap.push((cnt, c));
+            } else {
+                q.push_front(item);
+                break;
+            }
+        }
+
+        if let Some((cnt, c)) = heap.pop() {
+            if cnt > 1 {
+                q.push_back((time + n, cnt - 1, c));
+            }
+        }
+
+        time += 1;
+    }
+
+    time
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1() {
+        let tasks = vec!['A', 'A', 'A', 'B', 'B', 'B'];
+        let n = 2;
+        assert_eq!(least_interval(tasks, n), 8);
+    }
+
+    #[test]
+    fn test_2() {
+        let tasks = vec!['A', 'A', 'A', 'B', 'B', 'B'];
+        let n = 0;
+        assert_eq!(least_interval(tasks, n), 6);
+    }
+
+    #[test]
+    fn test_3() {
+        let tasks = vec!['A', 'A', 'A', 'A', 'A', 'A', 'B', 'C', 'D', 'E', 'F', 'G'];
+        let n = 2;
+        assert_eq!(least_interval(tasks, n), 16);
+    }
+}

src/readme.md

@@ -85,6 +85,7 @@
   - [x] [347. Top k frequent elements](../src/medium/top_k_frequent_elements.rs) -> [Problem Description](../src/medium/readme.md#347-top-k-frequent-elements)
   - [x] [424. Longest repeating character replacement](../src/medium/longest_repeating_character_replacement.rs) -> [Problem Description](../src/medium/readme.md#424-longest-repeating-character-replacement)
   - [x] [567. Permutation in string](../src/medium/permutation_in_string.rs) -> [Problem Description](../src/medium/readme.md#567-permutation-in-string)
+  - [x] [621. Task scheduler](../src/medium/task_scheduler.rs) -> [Problem Description](../src/medium/readme.md#621-task-scheduler)
   - [x] [739. Daily temperatures](../src/medium/daily_temperatures.rs) -> [Problem Description](../src/medium/readme.md#739-daily-temperatures)
   - [x] [853. Car fleet](../src/medium/car_fleet.rs) -> [Problem Description](../src/medium/readme.md#853-car-fleet)
   - [x] [875. Koko eating bananas](../src/medium/koko_eating_bananas.rs) -> [Problem Description](../src/medium/readme.md#875-koko-eating-bananas)

theory/categories/6.heap_priority_queue/readme.md

@@ -67,12 +67,12 @@ A priority queue can be implemented using a heap.
 - [x] [Last Stone Weight](https://leetcode.com/problems/last-stone-weight/) | Easy | [Solution](../../../src/easy/last_stone_weight.rs) | [Problem Description](../../../src/easy/readme.md#1046-last-stone-weight)
 - [x] [K Closest Points to Origin](https://leetcode.com/problems/k-closest-points-to-origin/) | Medium | [Solution](../../../src/medium/k_closest_points_to_origin.rs) | [Problem Description](../../../src/medium/readme.md#973-k-closest-points-to-origin)
 - [x] [Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array/) | Medium | [Solution](../../../src/medium/kth_largest_element_in_an_array.rs) | [Problem Description](../../../src/medium/readme.md#215-kth-largest-element-in-an-array)
-- [ ] [Task Scheduler](https://leetcode.com/problems/task-scheduler/) | Medium | [Solution](../../../src/medium/task_scheduler.rs) | [Problem Description](../../../src/medium/readme.md#621-task-scheduler)
+- [x] [Task Scheduler](https://leetcode.com/problems/task-scheduler/) | Medium | [Solution](../../../src/medium/task_scheduler.rs) | [Problem Description](../../../src/medium/readme.md#621-task-scheduler)
 - [ ] [Design Twitter](https://leetcode.com/problems/design-twitter/) | Medium | [Solution](../../../src/medium/design_twitter.rs) | [Problem Description](../../../src/medium/readme.md#355-design-twitter)
 - [ ] [Find Median from Data Stream](https://leetcode.com/problems/find-median-from-data-stream/) | Hard | [Solution](../../../src/hard/find_median_from_data_stream.rs) | [Problem Description](../../../src/hard/readme.md#295-find-median-from-data-stream)
 
 Category: `Heap / Priority Queue`
 Created on: 2023-11-02 21:12
-Last modified on: 2023-11-03 19:02
+Last modified on: 2023-11-03 22:13
 Status: In Progress
 Author: [David Bujosa](https://github.com/bujosa)