Sum of Left Leaves

sumOfLeftLeaves.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

int s(TreeNode* root) {
    int sum = 0;
    if (root->left) {
        if (root->left->left == nullptr && root->left->right == nullptr) {
            sum += root->left->val;
        }
        else {
            sum += s(root->left);
        }
    }
    if (root->right) {
        sum += s(root->right);
    }
    return sum;
}
class Solution {
public:
    int sumOfLeftLeaves(TreeNode* root) {
        if (root == nullptr) {
            return 0;
        }
        return s(root);
    }
};