Solve #226

Author: aylei

src/lib.rs

@@ -193,3 +193,4 @@ mod n0223_rectangle_area;
 mod n0222_count_complete_tree_nodes;
 mod n0224_basic_calculator;
 mod n0225_implement_stack_using_queues;
+mod n0226_invert_binary_tree;

src/n0226_invert_binary_tree.rs

@@ -0,0 +1,63 @@
+/**
+ * [226] Invert Binary Tree
+ *
+ * Invert a binary tree.
+ *
+ * Example:
+ *
+ * Input:
+ *
+ *
+ *      4
+ *    /   \
+ *   2     7
+ *  / \   / \
+ * 1   3 6   9
+ *
+ * Output:
+ *
+ *
+ *      4
+ *    /   \
+ *   7     2
+ *  / \   / \
+ * 9   6 3   1
+ *
+ * Trivia:<br />
+ * This problem was inspired by <a href="https://twitter.com/mxcl/status/608682016205344768" target="_blank">this original tweet</a> by <a href="https://twitter.com/mxcl" target="_blank">Max Howell</a>:
+ *
+ * <blockquote>Google: 90% of our engineers use the software you wrote (Homebrew), but you can&rsquo;t invert a binary tree on a whiteboard so f*** off.</blockquote>
+ *
+ */
+pub struct Solution {}
+use super::util::tree::{to_tree, TreeNode};
+
+// submission codes start here
+
+use std::cell::RefCell;
+use std::rc::Rc;
+impl Solution {
+    pub fn invert_tree(root: Option<Rc<RefCell<TreeNode>>>) -> Option<Rc<RefCell<TreeNode>>> {
+        if let Some(node) = root.clone() {
+            Solution::invert_tree(node.borrow().right.clone());
+            Solution::invert_tree(node.borrow().left.clone());
+            let left = node.borrow().left.clone();
+            let right = node.borrow().right.clone();
+            node.borrow_mut().left = right;
+            node.borrow_mut().right = left;
+        }
+        root
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_226() {
+        assert_eq!(Solution::invert_tree(tree![4,2,7,1,3,6,9]), tree![4,7,2,9,6,3,1]);
+    }
+}