Problem
Given the root of a binary tree, return the sum of all left leaves.
Input
root of a binary tree
Output
sum of all left leaves
Constraints
- 1 <= Number of Nodes in the Tree ≤ 1000
- -1000 <= Value of Nodes ≤ 1000
Sample Input
root = [5, 3, 7, 2, 6]
Sample Output
2
Solution
Approach: Recursion
class Solution {
public:
void solve (TreeNode* root, int &sum) {
if (root == NULL) {
return;
}
if (root->left != NULL) {
if (root->left->left == NULL && root->left->right == NULL) {
sum += root->left->val;
}
}
solve (root->left, sum);
solve (root->right, sum);
}
int sumOfLeftLeaves (TreeNode* root) {
int sum = 0;
solve(root, sum);
return sum;
}
};
Time complexity: O(n), n is the number of leaves in the binary tree