feat: add symmetric tree problem solution

Author: bujosa

src/easy/symmetric_tree.rs

@@ -0,0 +1,80 @@
+#![allow(dead_code)]
+use std::rc::Rc;
+use std::cell::RefCell;
+
+#[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
+    }
+  }
+}
+
+pub fn is_symmetric(root: Option<Rc<RefCell<TreeNode>>>) -> bool {
+    if root.is_none() {
+        return true;
+    }
+
+    let mut queue = std::collections::VecDeque::new();
+    
+    queue.push_back(root.clone());
+    queue.push_back(root.clone());
+    
+    while !queue.is_empty() {
+        let t1 = queue.pop_front().unwrap();
+        let t2 = queue.pop_front().unwrap();
+        if t1.is_none() && t2.is_none() {
+            continue;
+        }
+        if t1.is_none() || t2.is_none() {
+            return false;
+        }
+        let t1 = t1.unwrap();
+        let t2 = t2.unwrap();
+        let t1 = t1.borrow();
+        let t2 = t2.borrow();
+        if t1.val != t2.val {
+            return false;
+        }
+        queue.push_back(t1.left.clone());
+        queue.push_back(t2.right.clone());
+        queue.push_back(t1.right.clone());
+        queue.push_back(t2.left.clone());
+    }
+    true
+        
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_101() {
+        let mut t1 = TreeNode::new(1);
+        let mut t2 = TreeNode::new(2);
+        let mut t3 = TreeNode::new(2);
+        let  t4 = TreeNode::new(3);
+        let  t5 = TreeNode::new(4);
+        let  t6 = TreeNode::new(4);
+        let  t7 = TreeNode::new(3);
+        t3.left = Some(Rc::new(RefCell::new(t6)));
+        t3.right = Some(Rc::new(RefCell::new(t7)));
+        t2.left = Some(Rc::new(RefCell::new(t4)));
+        t2.right = Some(Rc::new(RefCell::new(t5)));
+        t1.left = Some(Rc::new(RefCell::new(t2)));
+        t1.right = Some(Rc::new(RefCell::new(t3)));
+        assert_eq!(is_symmetric(Some(Rc::new(RefCell::new(t1)))), true);
+    }
+}