problems(rs): add “530. Minimum Absolute Difference in BST”

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

problems/rs/minimum-absolute-difference-in-bst.rs

@@ -0,0 +1,64 @@
+// 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::cmp;
+use std::rc::Rc;
+
+struct Result {
+    min: i32,
+    d: i32,
+    max: i32,
+}
+
+impl Solution {
+    fn find_min_diff(root: Option<Rc<RefCell<TreeNode>>>) -> Result {
+        match root {
+            None => Result {
+                min: i32::MAX,
+                d: i32::MAX,
+                max: i32::MIN,
+            },
+            Some(r) => {
+                let l_min = Solution::find_min_diff(r.borrow().left.clone());
+                let r_min = Solution::find_min_diff(r.borrow().right.clone());
+
+                let mut current_d = i32::MAX;
+                if l_min.max != i32::MIN {
+                    current_d = (r.borrow().val - l_min.max).abs();
+                }
+                if r_min.min != i32::MAX {
+                    current_d = cmp::min(current_d, (r_min.min - r.borrow().val).abs());
+                }
+
+                Result {
+                    min: cmp::min(l_min.min, r.borrow().val),
+                    d: cmp::min(cmp::min(l_min.d, r_min.d), current_d),
+                    max: cmp::max(r.borrow().val, r_min.max),
+                }
+            }
+        }
+    }
+
+    pub fn get_minimum_difference(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let r = Solution::find_min_diff(root);
+
+        r.d
+    }
+}