problems(rs): add “2140. Solving Questions With Brainpower”

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

problems/solving-questions-with-brainpower.rs

@@ -0,0 +1,71 @@
+use std::cmp;
+
+#[derive(Debug)]
+struct Question {
+    answered: i64,
+    skipped: i64,
+}
+
+impl Question {
+    fn get_with_offset(stack: &Vec<Self>, offset: i64) -> i64 {
+        let i = stack.len() as i64 - offset - 1;
+        if i < 0 || i >= stack.len() as i64 {
+            return 0;
+        }
+
+        stack[i as usize].get()
+    }
+
+    pub fn new(q: &[i32], stack: &Vec<Self>) -> Self {
+        Self {
+            answered: q[0] as i64 + Self::get_with_offset(stack, q[1].into()),
+            skipped: Self::get_with_offset(stack, 0),
+        }
+    }
+
+    pub fn get(&self) -> i64 {
+        cmp::max(self.answered, self.skipped)
+    }
+}
+
+struct Solution {}
+impl Solution {
+    pub fn most_points(questions: Vec<Vec<i32>>) -> i64 {
+        let mut stack: Vec<Question> = vec![];
+
+        for input_q in questions.iter().rev() {
+            stack.push(Question::new(&input_q, &stack));
+        }
+
+        stack.last().unwrap().get()
+    }
+}
+
+fn main() {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_example_1() {
+        assert_eq!(
+            Solution::most_points(vec![vec![3, 2], vec![4, 3], vec![4, 4], vec![2, 5]]),
+            5
+        );
+    }
+
+    #[test]
+    fn test_example_2() {
+        assert_eq!(
+            Solution::most_points(vec![
+                vec![1, 1],
+                vec![2, 2],
+                vec![3, 3],
+                vec![4, 4],
+                vec![5, 5]
+            ]),
+            7
+        );
+    }
+}