Extra

-AdHoc
//Problem 1 (Pending): https://www.codechef.com/ICMT2019/problems/ICM08
//Problem 2: https://www.codechef.com/DCC2019/problems/DCC4

-BIT:
//Problem 1 (Count of distinct elements): https://www.hackerrank.com/contests/university-codesprint-4/challenges/unique-art/problem
//Solution 1: http://p.ip.fi/T9YM

-BFS
//Problem 1 (Multiple of number not containing some digits): https://www.spoj.com/problems/MULTII/

-Dealing with periodic repeats:

//Problem 1: https://codeforces.com/problemset/problem/173/A
//Problem 2: https://codeforces.com/contest/863/problem/C

-DP Problems:

//Problem 1: https://codeforces.com/contest/214/problem/D
//Problem 2: https://codeforces.com/problemset/problem/137/D
//Problem 3: https://codeforces.com/contest/229/problem/D
//Problem 4 (Mutually Dependent Recurrence): https://www.hackerrank.com/challenges/alien-languages/problem

-DP on Tree:
//Problem 1 (Minimum Vertex Cover + Number of Ways): https://www.spoj.com/problems/VOCV/ 
//Problem 2 (Number of subtrees with diameter <=K): https://www.spoj.com/problems/CNTTREE/
//Problem 3: https://codeforces.com/problemset/problem/815/C
//Problem 4 (Smaller to Larger merging): https://csacademy.com/contest/round-31/task/uniform-trees/

-DFS
//Problem 1 (Virtual Nodes):  https://codeforces.com/contest/821/problem/D
//Problem 2 (Missing Edges): https://codeforces.com/contest/920/problem/E

-DFS in 2D Grid:

//Problem 1: https://codeforces.com/contest/616/problem/C

-Flows:
//Problem 1 (Remove min number of vertices such that shortest path > K): https://icpcarchive.ecs.baylor.edu/index.php?option=onlinejudge&Itemid=99999999&category=311&page=show_problem&problem=2323

(Probability):
//Problem 1: https://codeforces.com/contest/513/problem/G2
//Problem 2: https://www.codechef.com/GWR17ROL/problems/KALADIN/
//Problem 3: https://codeforces.com/contest/280/problem/C

-GCD Inclusion Exclusion:

//Problem 1: https://codeforces.com/contest/548/problem/E
//Problem 2: https://codeforces.com/contest/839/problem/D
//Problem 3: https://www.codechef.com/ONIG2019/problems/BIT_CSUM/
//Solution 3: https://www.codechef.com/viewsolution/23676665

-Graph Theory:

//Problem 1 (Diameter logic): https://codeforces.com/contest/337/problem/D
//Problem 2 (Updating diameter): https://codeforces.com/problemset/problem/379/F
//Problem 3: https://codeforces.com/contest/1040/problem/E
//Problem 4: (DSU with Undo + Divide and Conquer): https://codeforces.com/contest/813/problem/F

-Math;

//Problem 1 (Pending): https://www.codechef.com/ICMT2019/problems/ICM06

-Smart Greedy:

//Problem 1: https://codeforces.com/contest/447/problem/D
//Problem 2 (Own Comparator): https://codeforces.com/contest/922/standings/friends/true

-Random Good Questions:

//Problem 1 (Math): https://codeforces.com/contest/396/problem/B
//Problem 2 (Binary Search with Consecutive Prefix Sums): https://codeforces.com/contest/837/problem/F
//Problem 3 (DP with Consecutive Prefix Sums): https://codeforces.com/contest/57/problem/C
//Problem 4 (Updating indices of a particular set): https://codeforces.com/contest/348/problem/C
//Problem 5 (Perfect Powers in a range): https://codeforces.com/problemset/problem/955/C
//Problem 6 (D length Jumps in Intervals): https://atcoder.jp/contests/arc068/tasks/arc068_c
//Problem 7 (Converging K points to Median - Cost): https://www.codechef.com/viewsolution/23192706
//Problem 8 (DFS with missing edges): https://codeforces.com/contest/653/problem/E
//Problem 9 (Interactive - Tree Labelling): https://codeforces.com/contest/1075/problem/D

-To Copy Paste in Future:
//Problem 1 (Getting a sequence of + and - by using a sequence of - operationss): http://p.ip.fi/6t7b
//Problem 2 (Number of ways to place elements such that adjacent are different and given L and R) : https://www.codechef.com/BLUP2019/problems/AHAPH/

Resources:
https://www.careerbless.com/aptitude/qa/permutations_combinations_imp7.php