20240221 Finsihed

src/problem/mod.rs

@@ -51,3 +51,4 @@ mod p102_binary_tree_level_order_traversal;
 mod p107_binary_tree_level_order_traversal_ii;
 mod p103_binary_tree_zigzag_level_order_traversal;
 mod p105_construct_binary_tree_from_preorder_and_inorder_traversal;
+mod p106_construct_binary_tree_from_inorder_and_postorder_traversal;

src/problem/p106_construct_binary_tree_from_inorder_and_postorder_traversal.rs

@@ -0,0 +1,98 @@
+/**
+ * [106] Construct Binary Tree from Inorder and Postorder Traversal
+ */
+pub struct Solution {}
+
+use crate::util::tree::{to_tree, TreeNode};
+
+// submission codes start here
+
+// 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::rc::Rc;
+impl Solution {
+    pub fn build_tree(inorder: Vec<i32>, postorder: Vec<i32>) -> Option<Rc<RefCell<TreeNode>>> {
+        if inorder.len() == 0 {
+            return None;
+        }
+
+        let root = Rc::new(RefCell::new(TreeNode::new(postorder[postorder.len() - 1])));
+
+        let mut stack = Vec::new();
+        stack.push(Rc::clone(&root));
+
+        let mut inorder_index = inorder.len() - 1;
+
+        for i in (0..postorder.len() - 1).rev() {
+            let post_order_value = postorder[i];
+            let mut node = Rc::clone(stack.last().unwrap());
+
+            if node.borrow().val != inorder[inorder_index] {
+                let new_node = Rc::new(RefCell::new(TreeNode::new(post_order_value)));
+                stack.push(Rc::clone(&new_node));
+                node.borrow_mut().right = Some(new_node);
+            } else {
+                while let Some(top) = stack.last() {
+                    if top.borrow().val == inorder[inorder_index] {
+                        node = Rc::clone(top);
+                        stack.pop();
+                        inorder_index -= 1;
+                    } else {
+                        break;
+                    }
+                }
+
+                let new_node = Rc::new(RefCell::new(TreeNode::new(post_order_value)));
+                stack.push(Rc::clone(&new_node));
+                node.borrow_mut().left = Some(new_node);
+            }
+        }
+
+        Some(root)
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_106() {
+        assert_eq!(
+            Solution::build_tree(vec![9, 3, 15, 20, 7], vec![9, 15, 7, 20, 3]),
+            to_tree(vec![
+                Some(3),
+                Some(9),
+                Some(20),
+                None,
+                None,
+                Some(15),
+                Some(7)
+            ])
+        );
+
+        assert_eq!(
+            Solution::build_tree(vec![-1], vec![-1]),
+            to_tree(vec![Some(-1)])
+        );
+    }
+}