LeetCode | Path Sum

题目

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.

              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.

递归的方法很简明，即DFS

代码

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;
		}
		return hasPathSum(root.left, sum - root.val)
				|| hasPathSum(root.right, sum - root.val);
	}
}