/**
* 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) {}
* };
*/
// Method 1.1
class Solution {
public:
vector<int> v;
bool findNums(TreeNode* node, int k) {
if(!node)
return false;
if(findNums(node->left, k))
return true;
if(binary_search(v.begin(),v.end(),k-node->val))
return true;
v.push_back(node->val);
return findNums(node->right, k);
};
bool findTarget(TreeNode* root, int k) {
return findNums(root, k);
}
};
// Method 1.2
class Solution {
public:
bool findTarget(TreeNode* root, int k) {
vector<int> v;
function<bool(TreeNode*)> findNums = [&](TreeNode* node){
if(!node) return false;
if(findNums(node->left)) return true;
if(binary_search(v.begin(),v.end(),k-node->val)) return true;
v.push_back(node->val);
return findNums(node->right);
};
return findNums(root);
}
};
// Method 2
class Solution {
public:
void inorder(TreeNode *root,vector<int> &arr) {
if(root == NULL)
return ;
inorder(root->left, arr);
arr.push_back(root->val);
inorder(root->right, arr);
}
bool findTarget(TreeNode* root, int k) {
vector<int> arr;
inorder(root,arr);
int i = 0,j = arr.size() - 1;
while(i < j) {
if(arr[i] + arr[j] == k)
return true;
if(arr[i] + arr[j] < k)
i++;
else
j--;
}
return false;
}
};