Hello, thank you for the editorial. Can you please help me with a test case in which my code is failing? I had used the approach in the editorial. So I am really confused where I am going wrong. I also tried various cases for an hour before giving up.
For the bonus problem which the Editorialist put forward:
We could maintain something like a parent array which holds the information about the node whose son it is. After completely scanning the input, we could randomly pick a node and move up the parent array until its God parent is detected. The node which we end up now, will be the root node and we will solve this problem rooting with this node.
Pseudocode: (Modifications only)
for i = 1 to N:
parent[i] = i
for i = 1 to N:
scan L,R
if(L != -1):
#usual code
parent[L] = parent[R] = i
else:
#usual code
root=1
while(parent[root] != root):
root = parent[root]
solve(root)
Time Complexity for finding root: O(logN)
where the worst case would be randomly selecting a leaf node and moving all the way up in logN steps.
@atharva_sarage, did you consider the case that the tree may not be perfectly balanced?
ie) left child = leaf and right a tree or vice versa. The condition still needs to be satisfied even if one side is a tree.
Hey, I still couldn’t understand the problem statement. How the strings are LL,RL,RR and how the input is converted to a binary tree. Can anyone please explain it properly, that would be really helpful !
@likecs In question the constraints has N>=2 but if N=2 then its impossible to build the tree because in question there is mentioned that “non-leaf: has exactly two sons — a left son and a right son”,for root is doesn’t satisfy, am i right to point it out?
Still its a interesting question
1 is the root.each line gives 2 children l and r or l=-1 means it’s a leaf.
So 1st line 3,5. so node 3,5 are children of 1. 2nd line is -1,2. so 2nd node is a leaf with value 2. 3 line is 2,4. so 3rd node has chilren 2,4 and so on.
Thanks for looking into the code. But the input that you give is invalid according to constraints as it is given in contraints for any child r is less than equal to number of leafs. So in this case L =2
So only possible values for childs is 1 and 2 not 5 and 7.
@ruddradev … I Was not able to implement it in contest but now if you are still stuck you can see my solution. It’s implemented exactly as stated in editorial.