How to Approach problem ??

1.  Firstly, read the question carefully. 
• If able to understand 100% => don't read the test case
• else read the test cases to get the feel
2. If not able to come up with any approach --> think of brute force -> then optimize
3. Categorize the problem where it lies
• Brute Force
• Maths
• Binary Search 
• Greedy
• DP
• Graph
• Bitwise stuffs
  
  
4. If given tree --> Visualize as shown in image (Think of BFS/DFS)
5. If given subarray -> can think of prefix sum or dp
   
   
6. If the code seems too lengthy => simplify => There must be a way
• Can use MATHS sometimes to simplify the expression or logic
  
  
7. If dp => lookout for the transition and state definition first
8. Whenever including edge case in anywhere always be 100% sure (even though you think its correct, it may be wrong).
9. Lookout for edge cases !!!
   
• If sure of solution => spend time on edge cases, even it seems trivial
  
  
10. If stuck 
• Check for negation of problem demand
• what will happen if include one by one 
• solve for small values
• look for trend and the overlapping portions (if TLE)
  
  
11. Try to simplify problem statement (if feels complex)
12. If remove subarray -> can use prefix + suffix array combination
13. If hard to find for equality --> find for inequality and adjust
• Example - Find no. of subarray whose product = k → let's say it's easy to find no. of subarray whose product ≤ k → ans = fun(k) - fun(k-1)