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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* deleteNode(TreeNode* root, int key) {
        if(root==nullptr) return root;
        
        if(key<root->val){
            root->left=deleteNode(root->left,key);

        }else if(key >root->val){
            root->right=deleteNode(root->right,key);
        }

        else if(key ==root->val){ //we found the node , now replace it with the min value from right subtree and recursively delete the min value
            if(!root->left) return root->right;
            else if(!root->right) return root->left;
            else if(root->left && root->right){
                TreeNode* tmp=root->right;
                while(tmp->left) tmp=tmp->left;
                root->val=tmp->val;
                root->right=deleteNode(root->right,tmp->val);
            }
        }
        return root;
    }
};