LeetCode "Sum Root to Leaf Numbers"

A typical DFS usage, no big deal:

class Solution {
public:    
    int dfs(TreeNode *p, int pval)
    {
        if( !p->left && !p->right )
        {
            int ssum = pval * 10 + p->val;            
            return ssum;
        }

        int rl = 0, rr = 0;
        if(p->left)  rl = dfs(p->left, pval * 10 + p->val);
        if(p->right) rr = dfs(p->right, pval * 10 + p->val);
        return rl + rr;
    }
    int sumNumbers(TreeNode *root) {
        int ret = 0;
        if(root)    ret = dfs(root, 0);
        return ret;
    }
};