20240214 Finished

src/problem/mod.rs

@@ -47,3 +47,4 @@ mod p94_binary_tree_inorder_traversal;
 mod p144_binary_tree_preorder_traversal;
 mod p145_binary_tree_postorder_traversal;
 mod p987_vertical_order_traversal_of_a_binary_tree;
+mod p102_binary_tree_level_order_traversal;

src/problem/p102_binary_tree_level_order_traversal.rs

@@ -0,0 +1,79 @@
+/**
+ * [102] Binary Tree Level Order Traversal
+ */
+pub struct Solution {}
+
+use crate::util::tree::{TreeNode, to_tree};
+
+// 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::rc::Rc;
+use std::cell::RefCell;
+use std::collections::VecDeque;
+
+impl Solution {
+    pub fn level_order(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<Vec<i32>> {
+        let root = if let Some(r) = root {
+            r
+        } else {
+            return vec![];
+        };
+
+        let mut result = Vec::new();
+        let mut queue = VecDeque::new();
+        queue.push_back(root);
+
+        while !queue.is_empty() {
+            let mut level = Vec::with_capacity(queue.len());
+            for _ in 0..queue.len() {
+                if let Some(node) = queue.pop_front() {
+                    level.push(node.borrow().val);
+
+                    if let Some(left) = &node.borrow().left {
+                        queue.push_back(Rc::clone(left));
+                    }
+
+                    if let Some(right) = &node.borrow().right {
+                        queue.push_back(Rc::clone(right));
+                    }
+                }
+            }
+
+            result.push(level);
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_102() {
+        assert_eq!(Solution::level_order(
+            to_tree(vec![Some(3), Some(9), Some(20), None, None, Some(15), Some(7)])
+        ), vec![vec![3], vec![9, 20], vec![15, 7]]);
+    }
+}