solve #112

Author: aylei

src/lib.rs

@@ -112,3 +112,4 @@ mod n0108_convert_sorted_array_to_binary_search_tree;
 mod n0109_convert_sorted_list_to_binary_search_tree;
 mod n0110_balanced_binary_tree;
 mod n0111_minimum_depth_of_binary_tree;
+mod n0112_path_sum;

src/n0112_path_sum.rs

@@ -0,0 +1,63 @@
+/**
+ * [112] Path Sum
+ *
+ * Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
+ * 
+ * Note: A leaf is a node with no children.
+ * 
+ * Example:
+ * 
+ * Given the below binary tree and sum = 22,
+ * 
+ * 
+ *       5
+ *      / \
+ *     4   8
+ *    /   / \
+ *   11  13  4
+ *  /  \      \
+ * 7    2      1
+ * 
+ * 
+ * return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
+ * 
+ */
+pub struct Solution {}
+use super::util::tree::{TreeNode, to_tree};
+
+// submission codes start here
+
+use std::rc::Rc;
+use std::cell::RefCell;
+use std::collections::VecDeque;
+impl Solution {
+    pub fn has_path_sum(root: Option<Rc<RefCell<TreeNode>>>, sum: i32) -> bool {
+        if root.is_none() { return false }
+        let mut deq = VecDeque::new();
+        deq.push_back((0, root.clone()));
+        while !deq.is_empty() {
+            if let Some((acc, Some(node))) = deq.pop_front() {
+                let acc = acc + node.borrow().val;
+                if node.borrow().left.is_none() && node.borrow().right.is_none() {
+                    if acc == sum { return true }
+                } else {
+                    deq.push_back((acc, node.borrow().left.clone()));
+                    deq.push_back((acc, node.borrow().right.clone()));
+                }
+            }
+        }
+        false
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_112() {
+        assert_eq!(Solution::has_path_sum(tree![5,4,8,11,null,13,4,7,2,null,null,null,1], 22), true);
+    }
+}