Path Sum III @LeetCode

PROBLEM :

You are given a binary tree in which each node contains an integer value.

Find the number of paths that sum to a given value.

The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).

The tree has no more than 1,000 nodes and the values are in the range -1,000,000 to 1,000,000.

Example:

root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8

      10
     /  \
    5   -3
   / \    \
  3   2   11
 / \   \
3  -2   1

Return 3. The paths that sum to 8 are:

1.  5 -> 3
2.  5 -> 2 -> 1
3. -3 -> 11

--------------------------------------------------------------------------------
SIMPLE c++ IMPLEMENTATION :
--------------------------------------------------------------------------------

/**
 * 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:
    int pathSum(TreeNode* root, int sum) {
        if(!root)
            return 0 ;
           
        return (PathCount(root,0,sum) + pathSum(root->left,sum) + pathSum(root->right,sum)) ;
    }
   
    int PathCount(TreeNode *root,int prev,int sum)
    {
        if(!root)
            return 0 ;
           
        int curr=prev+root->val ;

        return  ((curr==sum) + PathCount(root->left,curr,sum) + PathCount(root->right,curr,sum)) ;
    }
};

--------------------------------------------------------------------------------

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