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Notes

Two problems I face while solving algorithms

  1. mathematical analysis
  2. Pattern recognition

I have noticed I approach problems in a brute force manner. However, from solutions I have encoutered, I have learnt that I should try and find a pattern and see how that can be used to optimize my code.

Patterns I have noticed so far

  1. Rise, fall, valleys and peak patterns of numbers
  2. When there are sequential numbers that are scattered and you ned to find minimum actions to take a sorting algorithm will most likely be the clue.

Mathematical Tricks

  1. The Modulo (%) operator x + (y - (x % y)) will return the next highest multiple of y from x It can also be used to wrap around an array preventing the need of an IF statement idx % N will wrap around an array
  2. For any number K, the sum of 2 values (A & B) is evenly divisible by K if the sum of the remainders of A/K + B/K is K That is if (A%K) + (B%K) == K

PITFALLS

  1. Try not to confuse SUB-SET, SUB-SEQUENCE, SUB-ARRAY / SUB-STRING
  2. For sequential lists 1 <= a[i] <= n -- should not be confused with from 1 <= a[i] <= 10^x