[LintCode] Remove Node in Binary Search Tree

标签：

http://www.lintcode.com/en/problem/remove-node-in-binary-search-tree/#

Given a root ofBINARY Search Tree with unique value for each node.  Remove the node with given value. If there is no such a node with given value in theBINARY search tree, do nothing. You should keep the tree still aBINARY search tree after removal.

Example

Given binary search tree:

          5

       /    \

    3          6

/    \

2       4

Remove 3, you can either return:

          5

       /    \

    2          6

      \

         4

or :

          5

       /    \

    4          6

/  

2

先上代码，有时间了再给解析，此题是面试常考题，连微软亚洲研究院都出过该题..

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param root: The root of the binary search tree.
     * @param value: Remove the node with given value.
     * @return: The root of the binary search tree after removal.
     */
    TreeNode* removeNode(TreeNode* root, int value) {
         if (root == NULL) {
             return root;
         }
         
         int dummyValue;
         if (value != INT_MIN) {
             dummyValue = value + 1;
             TreeNode *dummyNode = new TreeNode(dummyValue);
             dummyNode->left = root;
             return removeNodeHelper(dummyNode, value)->left;
         } else {
             dummyValue = value - 1;
             TreeNode *dummyNode = new TreeNode(dummyValue);
             dummyNode->right = root;
             return removeNodeHelper(dummyNode, value)->right;
         }
    }
    
private:
    
    TreeNode *removeNodeHelper(TreeNode *root, int value) {
        if (root == NULL) {
            return NULL;
        }
        
        if (value < root->val) {
            root->left = removeNodeHelper(root->left, value);
        } else if (root->val < value) {
            root->right = removeNodeHelper(root->right, value);
        } else { // while equal, then delete, change the pointer
            if (root->left == NULL) {
                TreeNode *rightChild = root->right;
                delete root;
                return rightChild;
            }
            
            if (root->right == NULL) {
                TreeNode *leftChild = root->left;
                delete root;
                return leftChild;
            }
            
            // left child and right child all exsit
            TreeNode *childOfRight = findMinOfRight(root->right);
            
            TreeNode *childOfRightBak = new TreeNode(childOfRight->val);
            childOfRightBak->left = root->left;
            childOfRightBak->right = root->right;
            
            root->right = removeNodeHelper(root->right, childOfRight->val);
            delete root;
            
            return childOfRightBak;
        }
        
        return root;
    }
    
    TreeNode *findMinOfRight(TreeNode *root) {
        if (root->left == NULL) {
            return root;
        }
        
        return findMinOfRight(root->left);
    }
};

[LintCode] Remove Node in Binary Search Tree

标签：

原文地址：http://www.cnblogs.com/jianxinzhou/p/4544508.html