Merge k sorted array

typdef ka matlab samjh ni aaya?

google pe ye meaning hai The typedef is used to give data type a new name.

The typedef keyword allows the programmer to create new names for types

using typedef you can give a new name to existing type

now in this question

using typedef you have given a new name to pair<int,pair<int,int>> which is node
so instead of writing pair<int,pair<int,int>> every time you can write node instead of this large type