112. Path Sum | Leetcode solution

 112. Path Sum

Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path such that adding up all the values along the path equals targetSum.

A leaf is a node with no children.

 

Example 1:

Input: root = [5,4,8,11,null,13,4,7,2,null,null,null,1], targetSum = 22
Output: true
Explanation: The root-to-leaf path with the target sum is shown.

Example 2:

Input: root = [1,2,3], targetSum = 5
Output: false
Explanation: There two root-to-leaf paths in the tree:
(1 --> 2): The sum is 3.
(1 --> 3): The sum is 4.
There is no root-to-leaf path with sum = 5.

Example 3:

Input: root = [], targetSum = 0
Output: false
Explanation: Since the tree is empty, there are no root-to-leaf paths.

 

Constraints:

• The number of nodes in the tree is in the range [0, 5000].
• -1000 <= Node.val <= 1000
• -1000 <= targetSum <= 1000

solution:

/**

 * 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) {}

 * };

 */

class Solution {

public:

    bool hs(TreeNode *root , int ts , int sum)

    {    sum = sum + root->val;

        

        if( root->left == NULL && root->right ==NULL)

        {

            if(sum == ts)

                return true;

            else

                return false;

        }

            

        if(root->left != NULL && root->right != NULL)

            return hs(root->left , ts , sum) || hs(root->right , ts , sum);

     else

         if(root->left != NULL)

             return hs(root->left, ts,  sum);

      else

          if(root->right != NULL)

              return hs(root->right , ts , sum);

            

        return false;

    }

    bool hasPathSum(TreeNode* root, int targetSum) {

        

        int sum =0;

        if(root == NULL)

        {

                return false;

        }

        return hs(root , targetSum  , sum);

    }

};