day 23

Author: sachuverma

Leetcode Daily Challenge/August-2021/23. Two Sum IV - Input is a BST.cpp

@@ -0,0 +1,69 @@
+/*
+Two Sum IV - Input is a BST
+===========================
+
+Given the root of a Binary Search Tree and a target number k, return true if there exist two elements in the BST such that their sum is equal to the given target.
+
+Example 1:
+Input: root = [5,3,6,2,4,null,7], k = 9
+Output: true
+
+Example 2:
+Input: root = [5,3,6,2,4,null,7], k = 28
+Output: false
+
+Example 3:
+Input: root = [2,1,3], k = 4
+Output: true
+
+Example 4:
+Input: root = [2,1,3], k = 1
+Output: false
+
+Example 5:
+Input: root = [2,1,3], k = 3
+Output: true
+ 
+Constraints:
+The number of nodes in the tree is in the range [1, 104].
+-104 <= Node.val <= 104
+root is guaranteed to be a valid binary search tree.
+-105 <= k <= 105
+*/
+
+/**
+ * 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:
+    void dfs(TreeNode* root, vector<int>& arr){
+        if(!root) return;
+        dfs(root->left, arr);
+        arr.push_back(root->val);
+        dfs(root->right, arr);
+    }
+    
+    bool findTarget(TreeNode* root, int k) {
+        vector<int> arr;
+        dfs(root, arr);
+        
+        int i=0, j=arr.size()-1;
+        while(i < j) {
+            if(arr[i] + arr[j] == k) return true;
+            else if(arr[i] + arr[j] < k) i++;
+            else j--;
+        }
+        
+        return false;
+    }
+};
+

Leetcode Daily Challenge/August-2021/README.md

@@ -24,3 +24,5 @@
 | 19. | [Maximum Product of Splitted Binary Tree](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge-2021/615/week-3-august-15th-august-21st/3903/) | [cpp](./19.%20Maximum%20Product%20of%20Splitted%20Binary%20Tree.cpp) |
 | 20. | [Valid Sudoku](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge-2021/615/week-3-august-15th-august-21st/3904/)                            |                  [cpp](./20.%20Valid%20Sudoku.cpp)                   |
 | 21. | [Sudoku Solver](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge-2021/615/week-3-august-15th-august-21st/3905/)                            |                  [cpp](./20Sudoku%20Solver.%20.cpp)                   |
+| 23. | [Two Sum IV - Input is a BST](https://leetcode.com/explore/featured/card/august-leetcoding-challenge-2021/616/week-4-august-22nd-august-28th/3908/)                            |                  [cpp](./23Two%20Sum%20IV%20-%20Input%20is%20a%20BST.cpp)                   |
+| 24. | []()                            |                  [cpp](./24.cpp)                   |