Create sum-of-left-leaves.cpp

Author: kamyu104

C++/sum-of-left-leaves.cpp

@@ -0,0 +1,30 @@
+// Time:  O(n)
+// Space: O(h)
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    int sumOfLeftLeaves(TreeNode* root) {
+        return sumOfLeftLeavesHelper(root, false);
+    }
+
+private:
+    int sumOfLeftLeavesHelper(TreeNode* root, bool is_left) {
+        if (!root) {
+            return 0;
+        }
+        if (!root->left && !root->right) {
+            return is_left ? root->val : 0;
+        }
+        return sumOfLeftLeavesHelper(root->left, true) +
+               sumOfLeftLeavesHelper(root->right, false);
+    }
+};