Replace With Sum of Greater Nodes

Author: akashmodak97

Hacker Blocks/Replace With Sum of Greater Nodes.cpp

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+/* Hacker Blocks */
+/* Title - Replace With Sum of Greater Nodes */
+/* Created By - Akash Modak */
+/* Date - 19/09/2020 */
+
+// Given a binary search tree, replace each nodes' data with the sum of all nodes' which are greater or equal than it. Include the current node's data also.
+
+// Input Format
+// The first line contains a number n showing the length of the inorder array of BST. The next line contains n integers denoting the elements of the array.
+
+// Constraints
+// 2 ≤ N ≤ 10^3
+
+// Output Format
+// Print the preorder traversal of the new tree.
+
+// Sample Input
+// 7
+// 20 30 40 50 60 70 80
+// Sample Output
+// 260 330 350 300 150 210 80
+// Explanation
+// The original tree looks like
+
+//             50             
+//         /        \                
+//       30          70
+//     /    \       /   \ 
+//   20    40      60    80
+// We are supposed to replace the elements by the sum of elements larger than it.
+// 80 being the largest element remains unaffected .
+// 70 being the second largest element gets updated to 150 (70+80)
+// 60 becomes 210 (60 + 70 + 80)
+// 50 becomes 260 (50 + 60 + 70 + 80)
+// 40 becomes 300 (40 + 50 + 60 + 70 + 80)
+// 30 becomes 330 (30 + 40 + 50 + 60 + 70 + 80)
+// 20 becomes 350 (20 + 30 + 40 + 50 + 60 + 70 + 80)
+
+// The new tree looks like
+
+//            260             
+//         /        \                
+//      330         150
+//     /    \       /   \ 
+//   350    300   210    80
+// The Pre-Order traversal (Root->Left->Right) looks like :
+// 260 330 350 300 150 210 80.
+
+#include<bits/stdc++.h>
+using namespace std;
+int temp;
+class node{
+	public:
+	int data;
+	node* left,*right;
+	node(int d){
+		data=d;
+		left=right=NULL;
+	}
+};
+node* bst(int *a,int start,int end){
+	if(start>end)
+	return NULL;
+
+	int mid = start + (end-start)/2;
+	node* root = new node(a[mid]);
+	root->left = bst(a,start,mid-1);
+	root->right = bst(a,mid+1,end);
+	return root;
+}
+void update(node* root,int &sum){
+	if(root==NULL)
+	return ;
+
+	// if(root->data == temp)
+	// return root->data;
+
+	update(root->right,sum);
+	// root->data = rightSum + root->data;
+	sum = sum+root->data;
+	root->data = sum;
+	update(root->left,sum);
+}
+void preorder(node* root){
+	if(root==NULL)
+	return;
+
+	cout<<root->data<<" ";
+	preorder(root->left);
+	preorder(root->right);
+}
+int main() {
+	node *root = NULL;
+	int n;
+	cin>>n;
+	int a[n];
+	for(int i=0;i<n;i++)
+	{
+		cin>>a[i];
+		if(i==n-1)
+		temp = a[i];
+	}
+
+	root = bst(a,0,n-1);
+	int sum=0;
+	update(root,sum);
+	preorder(root);
+	return 0;
+}