From now on, I will add some topic wise problems which I face regularly. I think it will help new commers like me. Thank you.

1.Cumulative sum/ prefix sum :

(https://codeforces.com/problemset/problem/363/B) (https://codeforces.com/problemset/problem/313/B) (https://codeforces.com/problemset/problem/1363/B) (https://codeforces.com/problemset/problem/433/B) (https://codeforces.com/problemset/problem/296/C) (https://codeforces.com/problemset/problem/816/B) (https://codeforces.com/problemset/problem/1341/B) (https://codeforces.com/problemset/problem/961/B) (https://codeforces.com/problemset/problem/276/C) (https://codeforces.com/problemset/problem/1678/B1) (https://codeforces.com/problemset/problem/1678/B1) (https://www.spoj.com/problems/CSUMQ/en/) (https://www.spoj.com/problems/RANGESUM/en/) (https://www.codechef.com/problems/QUALPREL) (https://www.codechef.com/problems/PTMSSNG) (https://www.codechef.com/problems/MEX) (https://www.codechef.com/problems/PTMSSNG) (https://www.eolymp.com/en/problems/6959) (https://onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=924)