In 1 Month it is next to impossible because there are around 10 CSE subjects and “Maths” to prepare,and Prepare means thoroughly prepare because there will be theoretical questions and it can be from any topic of respective subjects.
Main focus should be on DS(Trees,Graphs),CN(DLL,Network Layer),OS(Memory Management),DBMS(ERD,Normalization),DE(Combinational and Sequential),TOC(Regular Expression and Grammar,Automata).