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  • [leetcode-669-Trim a Binary Search Tree]

    Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.

    Example 1:

    Input: 
        1
       / 
      0   2
    
      L = 1
      R = 2
    
    Output: 
        1
          
           2
    

    Example 2:

    Input: 
        3
       / 
      0   4
       
        2
       /
      1
    
      L = 1
      R = 3
    
    Output: 
          3
         / 
       2   
      /
     1

    思路:

    递归即可。

    TreeNode* trimBST(TreeNode* root, int L, int R)
    {
        if (root == NULL || L>R)return NULL;
        if (root->val == L)
        {
            root->left = NULL;
            root->right = trimBST(root->right, L + 1, R);
            return root;
        }
        else if (root->val == R)
        {
            root->right = NULL;
            root->left = trimBST(root->left, L, R - 1);
            return root;
        }
        else if (root->val<L)return trimBST(root->right, L, R);    
        else if (root->val>R)return trimBST(root->left, L, R);
        else
        {
            root->left = trimBST(root->left, L, root->val - 1);
            root->right = trimBST(root->right, root->val + 1, R);
            return root;
        }
    
    }
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  • 原文地址:https://www.cnblogs.com/hellowooorld/p/7469224.html
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