LeetCode——Path Sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and  sum = 22 ,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \      \
        7    2      1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

» Solve this problem

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
private:
    bool equals;
    
    void traversal(TreeNode *root, int sum, int cur) {
        if (root->left == NULL && root->right == NULL) {
            if (cur + root->val == sum) {
                equals = true;
            }            
        }
        else {
            if (!equals && root->left != NULL) {
                traversal(root->left, sum, cur + root->val);            
            }
            if (!equals && root->right != NULL) {
                traversal(root->right, sum, cur + root->val);            
            }            
        }
    }
    
public:
    bool hasPathSum(TreeNode *root, int sum) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        equals = false;
        if (root != NULL) {
            traversal(root, sum, 0);
        }
        return equals;
    }
};