problems(rs): add “1964. Find the Longest Valid Obstacle Course at Each Position”

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/find-the-longest-valid-obstacle-course-at-each-position.rs

@@ -0,0 +1,54 @@
+struct Solution {}
+impl Solution {
+    pub fn longest_obstacle_course_at_each_position(obstacles: Vec<i32>) -> Vec<i32> {
+        let size = obstacles.len();
+
+        let mut lengths: Vec<i32> = vec![1; size];
+        let mut longest_increasing: Vec<i32> = vec![];
+
+        for (i, &height) in obstacles.iter().enumerate() {
+            let idx = longest_increasing.partition_point(|&x| x <= height);
+
+            if idx == longest_increasing.len() {
+                longest_increasing.push(height);
+            } else {
+                longest_increasing[idx] = height;
+            }
+
+            lengths[i] = (idx + 1) as i32;
+        }
+
+        lengths
+    }
+}
+
+fn main() {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn example_1() {
+        assert_eq!(
+            Solution::longest_obstacle_course_at_each_position(vec![1, 2, 3, 2]),
+            vec![1, 2, 3, 3]
+        );
+    }
+
+    #[test]
+    fn example_2() {
+        assert_eq!(
+            Solution::longest_obstacle_course_at_each_position(vec![2, 2, 1]),
+            vec![1, 2, 1]
+        );
+    }
+
+    #[test]
+    fn example_3() {
+        assert_eq!(
+            Solution::longest_obstacle_course_at_each_position(vec![3, 1, 5, 6, 4, 2]),
+            vec![1, 1, 2, 3, 2, 2]
+        );
+    }
+}