Path Sum — Root-to-Leaf DFS with Running Remainder

# Python
def hasPathSum(root, target):
    if not root: return False
    if not root.left and not root.right: return root.val == target
    return hasPathSum(root.left, target-root.val) or hasPathSum(root.right, target-root.val)

// Java
public boolean hasPathSum(TreeNode root, int targetSum) {
    if (root==null) return false;
    if (root.left==null&&root.right==null) return root.val==targetSum;
    return hasPathSum(root.left,targetSum-root.val)||hasPathSum(root.right,targetSum-root.val);
}