problems(rs): add “1161. Maximum Level Sum of a Binary Tree”

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

problems/rs/maximum-level-sum-of-a-binary-tree.rs

@@ -0,0 +1,60 @@
+// Definition for a binary tree node.
+// #[derive(Debug, PartialEq, Eq)]
+// pub struct TreeNode {
+//   pub val: i32,
+//   pub left: Option<Rc<RefCell<TreeNode>>>,
+//   pub right: Option<Rc<RefCell<TreeNode>>>,
+// }
+//
+// impl TreeNode {
+//   #[inline]
+//   pub fn new(val: i32) -> Self {
+//     TreeNode {
+//       val,
+//       left: None,
+//       right: None
+//     }
+//   }
+// }
+
+use std::cell::RefCell;
+use std::convert::TryInto;
+use std::rc::Rc;
+
+impl Solution {
+    fn max_sum(levels: &mut Vec<i32>, level: usize, root: Option<Rc<RefCell<TreeNode>>>) {
+        if root == None {
+            return;
+        }
+
+        let r = root.unwrap();
+
+        if level >= levels.len() {
+            levels.resize(level + 1, 0);
+        }
+        levels[level] += r.borrow().val;
+
+        Solution::max_sum(levels, level + 1, r.borrow().left.clone());
+        Solution::max_sum(levels, level + 1, r.borrow().right.clone());
+    }
+
+    pub fn max_level_sum(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut levels = vec![];
+
+        Solution::max_sum(&mut levels, 0, root);
+
+        levels
+            .iter()
+            .enumerate()
+            .fold((0, i32::MIN), |(max_l, max_s), (l, s)| {
+                if *s > max_s {
+                    (l + 1, *s)
+                } else {
+                    (max_l, max_s)
+                }
+            })
+            .0
+            .try_into()
+            .unwrap()
+    }
+}