IsPalindrome returns True if given string is a palindrome uses a two pointers which start from both ends of the string comparing and moving towards the middle of the string O(n) time, O(1) space.

maxProfit returns the maximum profit given the prices.

mimimumwindowsort find minumum window when sorted will sort the whole slice two pointers approach O(n) time and O(1) space.

two_numbers_target_sum given slice and target return true if 2 numbers sum up to the target O(n) time and O(n) space.

1<<31 - 1 or 1<<63 - 1.

1<<32 - 1 or 1<<64 - 1.

-1 << 31 or -1 << 63.

32 or 64.