删除二叉查找树的节点-LintCode

/**
* 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) {
// write your code here
if (!root)
return root;
TreeNode *cur = root, *par = NULL;
while (cur&&cur->val != value) {
par = cur;
if (cur->val > value)
cur = cur->left;
else if (cur->val < value)
cur = cur->right;
}
if (!cur)   //此时cur=NULL，表示没有找到val=value节点
return root; // do nothing
if (cur->left&&cur->right) { //找的的节点既有左孩子又有有孩子
TreeNode *son = cur->left, *sp = cur;
while (son->right) {
sp = son;
son = son->right;
} //son就是cur左子树种val最大的节点
cur->val = son->val; //把值赋值cur，这就完成了对cur操作
cur = son;
par = sp; //归根揭底，是要删除cur,但是cur赋值后，要删除左子树的最大点
}
TreeNode *dummy;
if(cur->right) // cur只右子树
dummy = cur->right;
else
dummy = cur->left;
if (cur == root) //cur就是根节点
root = dummy;
else {  //cur不是根节点，则par就为cur的父节点
if (par->left == cur)
par->left = dummy;
else
par->right = dummy;
}
delete cur;
return root;
}
};