1665. Minimum Initial Energy to Finish Tasks: RETRY, credit: https://leetcode.com/problems/minimum-initial-energy-to-finish-tasks/solutions/1000272/rust-sorted-greedy-o-n-log-n/

Author: tan-wei

src/solution/mod.rs

@@ -1255,3 +1255,4 @@ mod s1659_maximize_grid_happiness;
 mod s1662_check_if_two_string_arrays_are_equivalent;
 mod s1663_smallest_string_with_a_given_numeric_value;
 mod s1664_ways_to_make_a_fair_array;
+mod s1665_minimum_initial_energy_to_finish_tasks;

src/solution/s1665_minimum_initial_energy_to_finish_tasks.rs

@@ -0,0 +1,125 @@
+/**
+ * [1665] Minimum Initial Energy to Finish Tasks
+ *
+ * You are given an array tasks where tasks[i] = [actuali, minimumi]:
+ *
+ * 	actuali is the actual amount of energy you spend to finish the i^th task.
+ * 	minimumi is the minimum amount of energy you require to begin the i^th task.
+ *
+ * For example, if the task is [10, 12] and your current energy is 11, you cannot start this task. However, if your current energy is 13, you can complete this task, and your energy will be 3 after finishing it.
+ * You can finish the tasks in any order you like.
+ * Return the minimum initial amount of energy you will need to finish all the tasks.
+ *  
+ * Example 1:
+ *
+ * Input: tasks = [[1,2],[2,4],[4,8]]
+ * Output: 8
+ * Explanation:
+ * Starting with 8 energy, we finish the tasks in the following order:
+ *     - 3rd task. Now energy = 8 - 4 = 4.
+ *     - 2nd task. Now energy = 4 - 2 = 2.
+ *     - 1st task. Now energy = 2 - 1 = 1.
+ * Notice that even though we have leftover energy, starting with 7 energy does not work because we cannot do the 3rd task.
+ * Example 2:
+ *
+ * Input: tasks = [[1,3],[2,4],[10,11],[10,12],[8,9]]
+ * Output: 32
+ * Explanation:
+ * Starting with 32 energy, we finish the tasks in the following order:
+ *     - 1st task. Now energy = 32 - 1 = 31.
+ *     - 2nd task. Now energy = 31 - 2 = 29.
+ *     - 3rd task. Now energy = 29 - 10 = 19.
+ *     - 4th task. Now energy = 19 - 10 = 9.
+ *     - 5th task. Now energy = 9 - 8 = 1.
+ * Example 3:
+ *
+ * Input: tasks = [[1,7],[2,8],[3,9],[4,10],[5,11],[6,12]]
+ * Output: 27
+ * Explanation:
+ * Starting with 27 energy, we finish the tasks in the following order:
+ *     - 5th task. Now energy = 27 - 5 = 22.
+ *     - 2nd task. Now energy = 22 - 2 = 20.
+ *     - 3rd task. Now energy = 20 - 3 = 17.
+ *     - 1st task. Now energy = 17 - 1 = 16.
+ *     - 4th task. Now energy = 16 - 4 = 12.
+ *     - 6th task. Now energy = 12 - 6 = 6.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= tasks.length <= 10^5
+ * 	1 <= actual​i <= minimumi <= 10^4
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/minimum-initial-energy-to-finish-tasks/
+// discuss: https://leetcode.com/problems/minimum-initial-energy-to-finish-tasks/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    // Credit: https://leetcode.com/problems/minimum-initial-energy-to-finish-tasks/solutions/1000272/rust-sorted-greedy-o-n-log-n/
+    pub fn minimum_effort(tasks: Vec<Vec<i32>>) -> i32 {
+        let mut tasks = tasks;
+
+        tasks.sort_unstable_by_key(|task| task[1] - task[0]);
+
+        let mut result = 0;
+        for task in tasks {
+            result += task[0];
+            if result < task[1] {
+                result += (task[1] - result);
+            }
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1665_example_1() {
+        let tasks = vec![vec![1, 2], vec![2, 4], vec![4, 8]];
+
+        let result = 8;
+
+        assert_eq!(Solution::minimum_effort(tasks), result);
+    }
+
+    #[test]
+    fn test_1665_example_2() {
+        let tasks = vec![
+            vec![1, 3],
+            vec![2, 4],
+            vec![10, 11],
+            vec![10, 12],
+            vec![8, 9],
+        ];
+
+        let result = 32;
+
+        assert_eq!(Solution::minimum_effort(tasks), result);
+    }
+
+    #[test]
+    fn test_1665_example_3() {
+        let tasks = vec![
+            vec![1, 7],
+            vec![2, 8],
+            vec![3, 9],
+            vec![4, 10],
+            vec![5, 11],
+            vec![6, 12],
+        ];
+
+        let result = 27;
+
+        assert_eq!(Solution::minimum_effort(tasks), result);
+    }
+}