PathSum.java

/** 
 * 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.
 */

public class PathSum {
	public boolean hasPathSum(TreeNode root, int sum) {
		if (root == null)
			return false;
		if (root.left == null && root.right == null && root.val == sum)
			return true;
		boolean l = root.left != null ? hasPathSum(root.left, sum - root.val)
				: false;
		boolean r = root.right != null ? hasPathSum(root.right, sum - root.val)
				: false;
		return l || r;
	}
}