leetcode Path Sum

/**
 * 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:
    bool hasPathSum(TreeNode* root, int sum) {
        if (root==NULL) return 0;
        queue<TreeNode*> q;
        TreeNode* r=root;
        q.push(r);
        while(!q.empty())
        {
            r = q.front();
            q.pop();
            if (r->left==NULL && r->right==NULL && r->val==sum) return true; // r is a leaf.
            else{
                if (r->left!=NULL) { r->left->val +=r->val; q.push(r->left);};
                if (r->right!=NULL){ r->right->val+=r->val; q.push(r->right);};
            }

        }
        return false;
    }
};