Array - linear data structure

• index(pointer) manipulation
• check bound in loop
• skip element to avoid duplicate
• element remove, replace, partation
• use HashMap to cache data
• two pointers used on sorted array
• math logic usually related with swap and reverse
• 2D index manipulation
• use boolean array to cache used or visited state
• consider each element and then combine the result
• digits manipulation, use of a carry state
• int[] arr = new int[n+1]
• In place manipulation
  • use one pointer to move
  • use two pointers to swap
  • use value to store state, 0 or 1, or use equations to generate multiply states
• index usually involved with ‘+1’ or ‘-1’
• usage of sum
• two pass, forward and backword
• shift k position – triple reversion – (n-k)(1),k(2), n(3)
• slidig window and Map or Set or TreeMap or TreeSet(ceiling(x), floor(x))
• update min1 and min2 pointer