How to get 5 start rating from 2 star rating in codechef in 1 month.

First of all you need to master your skills in any one language, for example in C++ you should be familiar with STL. Look I have done a similar thing, I first build a base by learning a language that was C++, then I took CLRS in and completed it but while doing this book I regularly competed in Codechef Long Challenge (with full devotion) and sometimes in CF short contests too ( which should also be done regularly), then, I started searching problems using those algorithms, since you have read CLRS you would be having good skills in time complexity analysis of algorithms so you hardly need one or two months to reach a level that solves ad-hoc problems easily, by regulary competing in coding contests.

The most important thing is practice, you should practice hard regularly.

After you finished practicing algorithms of CLRS, you should then jump to problems involving data structures like-

1. LCA

2. Centroid Decomposition

3. Heavy Light Decomposition

4. Persistence

5. Simplex Algorithm (you should try this, its okay if you don’t, because nobody prepares problem for this)

6. Dynamic programming optimizations

7. Link-cut trees

Of course finishing practice on algorithms of CLRS, themselves, may take months. The ones which I feel are frequently used and must be practiced are-

0. Binary search

1. Dijkstra’s Algorithm

2. Minimum Spanning Tree

3. Dfs and bfs

3. Number theoretic algorithms like primality testing and heavy modular mathematics.

4. Disjoint set union

5. KMP string matching

6. Segment trees (and Fenwick trees not in CLRS)

7. Dynamic programming

8. Convex hull computation

9. FFT

Other helpful topics

1. Bitmasking

There are plenty of other topics and if you do regularly, you could yourself figure out, what is required.

Well of course yes if you know how to solve problems involving above topics then there is no doubt that at that moment you are 5-star at codechef 

Thank you.