两数之和 IV - 输入 BST——Leetcode

代码实现:

public class FindTarget {


    public boolean findTarget(TreeNode root, int k) {
        if (root == null) return false;
        Map hashMap = new HashMap<>();
        return findTarget(root, k, hashMap);
    }


    public boolean findTarget(TreeNode root, int k, Map hashMap) {
        if (root == null) return false;
        if (hashMap.containsKey(root.val)){
            return true;
        }else {
            hashMap.put(k - root.val,true);
        }

        return findTarget(root.left, k, hashMap) || findTarget(root.right, k, hashMap);
    }

}