> For the complete documentation index, see [llms.txt](https://gopavasanth.gitbook.io/code/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gopavasanth.gitbook.io/code/sde-problems/untitled.md).

# Day 20: (Binary Search Tree)

[**Search given Key in BST**](https://leetcode.com/problems/search-in-a-binary-search-tree/submissions/)\
**Solved on: Aug 5th 2020**

```cpp
TreeNode* searchBST(TreeNode* root, int val) {
    if (root == NULL) {
        return NULL;
    }

    if (val > root->val) {
        return searchBST(root->right, val);
    } else if (val < root->val) {
        return searchBST(root->left, val);
    } else if (root->val == val) {
        return root;
    }
    return NULL;
}

```

[**Find the inorder predecessor/successor of a given Key in BST.** ](https://practice.geeksforgeeks.org/problems/predecessor-and-successor/1)\
Solved on Aug 6th 2020

```cpp
void findPreSuc(Node* root, Node*& pre, Node*& suc, int key) {
    if (root==NULL) {
        return ;
    }
    if (root->key == key) {
        if (root->right != NULL) {
            Node *temp = root->right;
            while (temp->left){
                temp=temp->left;
            }
            suc = temp;
        }
        if (root->left != NULL) {
            Node *temp = root->left;
            while (temp->right){
                temp=temp->right;
            }
            pre = temp;
        }
        return ;
    }
    if (key < root->key) {
        suc = root;
        findPreSuc(root->left,pre, suc, key);
    } else {
        pre = root;
        findPreSuc(root->right,pre, suc, key);
    }
}
```