List of good problems to solve to improve combinatorics in Competitive Programming in 2021 ?

Question

I want a very good list of problems so I can improve in an awesome manner ! :-)

Answer 1

Study combinatorics from here : 

1)https://www.hackerearth.com/practice/math/combinatorics/basics-of-combinatorics/tutorial/ 

2)https://www.mathsisfun.com/combinatorics/combinations-permutations.html 

3)https://www.hackerearth.com/practice/math/combinatorics/inclusion-exclusion/tutorial/ 

• Fundamentals
  • Finding Power of Factorial Divisor
  • Binomial Coefficients
  • Catalan Numbers
• Techniques
  • The Inclusion-Exclusion Principle
  • Burnside's lemma / Pólya enumeration theorem
  • Stars and bars
  • Generating all KK-combinations
• Tasks
  • Placing Bishops on a Chessboard
  • Balanced bracket sequences
  • Counting labeled graphs

https://www.comp.nus.edu.sg/~stevenha/myteaching/competitive_programming/cp1.pdf

 

Problems to practice :

Part-1 : 

https://codeforces.com/problemset/problem/1462/E2

https://codeforces.com/problemset/problem/1442/B

https://codeforces.com/problemset/problem/1444/B

https://codeforces.com/problemset/problem/1422/C

https://codeforces.com/problemset/problem/1420/D

https://codeforces.com/problemset/problem/1400/D

https://codeforces.com/problemset/problem/1329/B

https://codeforces.com/problemset/problem/1279/D

https://codeforces.com/problemset/problem/1301/C

Part-2: 

1)https://atcoder.jp/contests/hhkb2020/tasks/hhkb2020_e

2)https://www.codechef.com/FCF32020/problems/PATHWAY

3)https://www.codechef.com/INFY20B/problems/RRUN

4)https://www.codechef.com/COOK92A/problems/CO92REST 

5)https://codeforces.com/contest/1391/problem/C

2)https://codeforces.com/problemset/problem/1344/A

3)https://codeforces.com/contest/1327/problem/E

4)https://www.codechef.com/problems/RECNDSUB(VanderMonde’s identity)

5)https://codeforces.com/problemset/problem/1342/C

6)https://www.codechef.com/LTIME83A/problems/MEXUM

7)https://www.codechef.com/COOK110A/problems/ANGGRA

8)https://www.codechef.com/LTIME66A/problems/BPS

9)https://www.codechef.com/SNCKQL19/problems/TEAMMATE

10)https://www.codechef.com/SNCK1B19/problems/MAXPRODU

11)https://www.codechef.com/DEC19A/problems/BINXOR

12) https://codeforces.com/contest/1207/problem/D