20240222 Finished

src/problem/mod.rs

@@ -52,3 +52,4 @@ 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;
+mod p889_construct_binary_tree_from_preorder_and_postorder_traversal;

src/problem/p889_construct_binary_tree_from_preorder_and_postorder_traversal.rs

@@ -0,0 +1,100 @@
+/**
+ * [889] Construct Binary Tree from Preorder and Postorder Traversal
+ */
+pub struct Solution {}
+
+use tokio::time::error::Elapsed;
+
+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::collections::HashMap;
+use std::rc::Rc;
+impl Solution {
+    pub fn construct_from_pre_post(
+        preorder: Vec<i32>,
+        postorder: Vec<i32>,
+    ) -> Option<Rc<RefCell<TreeNode>>> {
+        let mut post_order_map = HashMap::new();
+
+        for (key, value) in postorder.iter().enumerate() {
+            post_order_map.insert(*value, key);
+        }
+
+        fn dfs(
+            pre_left: usize,
+            pre_right: usize,
+            post_left: usize,
+            post_right: usize,
+            post_order_map: &HashMap<i32, usize>,
+            preorder: &Vec<i32>,
+            postorder: &Vec<i32>,
+        ) -> Option<Rc<RefCell<TreeNode>>> {
+            if pre_left > pre_right {
+                return None;
+            }
+
+            let left_count = if pre_left < pre_right {
+                post_order_map[&preorder[pre_left + 1]] - post_left + 1
+            } else {
+                0
+            };
+
+            let new_node = Rc::new(RefCell::new(TreeNode::new(preorder[pre_left])));
+            new_node.borrow_mut().left = dfs(
+                pre_left + 1,
+                pre_left + left_count,
+                post_left,
+                post_left + left_count - 1,
+                post_order_map,
+                preorder,
+                postorder,
+            );
+            new_node.borrow_mut().right = dfs(
+                pre_left + left_count + 1,
+                pre_right,
+                post_left + left_count,
+                post_right - 1,
+                post_order_map,
+                preorder,
+                postorder,
+            );
+
+            Some(new_node)
+        };
+
+        let n = preorder.len();
+        dfs(0, n - 1, 0, n - 1, &post_order_map, &preorder, &postorder)
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_889() {}
+}