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  • 653. Two Sum IV

    Given a Binary Search Tree and a target number, return true if there exist two elements in the BST such that their sum is equal to the given target.

    Example 1:

    Input: 
        5
       / 
      3   6
     /    
    2   4   7
    
    Target = 9
    
    Output: True

    Example 2:

    Input: 
        5
       / 
      3   6
     /    
    2   4   7
    
    Target = 28
    
    Output: False

     1     private boolean dfs(TreeNode root, HashSet<Integer> set, int k)
     2     {
     3         if (root == null) return false;
     4         if (set.contains(k-root.val)) return true;
     5         set.add(root.val);
     6         return dfs(root.left,set,k) || dfs(root.right,set,k);
     7     }
     8     
     9     public boolean findTarget(TreeNode root, int k) {
    10         HashSet<Integer> set = new HashSet<>();
    11         return dfs(root,set,k);        
    12     }
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  • 原文地址:https://www.cnblogs.com/wzj4858/p/7710746.html
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