path sum 3 solution

pathSum.java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int pathSum(TreeNode root, int targetSum) {
        return getSubTress(root, targetSum, new ArrayList<>());
    }

    public int getSubTress(TreeNode root, long targetSum, List<Integer> path) {

        if (root == null) return 0;

        path.add(root.val);

        int pathCount = 0;
        long sum = 0;
        for (int i = path.size() - 1; i >= 0; i--) {
            sum += path.get(i);
            if (sum == targetSum) pathCount += 1;
        }

        pathCount += getSubTress(root.left, targetSum, path);
        pathCount += getSubTress(root.right, targetSum, path);

        path.remove(path.size() - 1);

        return pathCount;
    }
}