Solve #257

Author: aylei

src/lib.rs

@@ -205,3 +205,4 @@ mod n0238_product_of_array_except_self;
 mod n0239_sliding_window_maximum;
 mod n0241_different_ways_to_add_parentheses;
 mod n0242_valid_anagram;
+mod n0257_binary_tree_paths;

src/n0257_binary_tree_paths.rs

@@ -0,0 +1,79 @@
+/**
+ * [257] Binary Tree Paths
+ *
+ * Given a binary tree, return all root-to-leaf paths.
+ *
+ * Note: A leaf is a node with no children.
+ *
+ * Example:
+ *
+ *
+ * Input:
+ *
+ *    1
+ *  /   \
+ * 2     3
+ *  \
+ *   5
+ *
+ * Output: ["1->2->5", "1->3"]
+ *
+ * Explanation: All root-to-leaf paths are: 1->2->5, 1->3
+ *
+ */
+pub struct Solution {}
+use super::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 binary_tree_paths(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<String> {
+        let mut res = Vec::new();
+        Solution::helper(root, "".to_owned(), &mut res);
+        res
+    }
+
+    fn helper(root: Option<Rc<RefCell<TreeNode>>>, path: String, res: &mut Vec<String>) {
+        if let Some(inner) = root {
+            if inner.borrow().left.is_none() && inner.borrow().right.is_none() {
+                res.push(format!("{}{}", path, inner.borrow().val));
+            } else {
+                let path = format!("{}{}->", path, inner.borrow().val);
+                Solution::helper(inner.borrow().left.clone(), path.clone(), res);
+                Solution::helper(inner.borrow().right.clone(), path, res);
+            }
+        }
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_257() {
+        assert_eq!(Solution::binary_tree_paths(tree![1,2,3,null,5]), vec_string!["1->2->5", "1->3"]);
+    }
+}