517 Super Washing Machines

• the least steps we need to eventually finish this process is determined by the peak of abs(cnt) (accumulative count of gain/lose array) and the max of “gain/lose” array. >For a single machine, necessary operations is to transfer dresses from one side to another until sum of both sides and itself reaches the average number. We can calculate (required dresses) - (contained dresses) of each side as L and R:

L > 0 && R > 0: both sides lacks dresses, and we can only export one dress from current machines at a time, so result is abs(L) + abs® L < 0 && R < 0: both sides contains too many dresses, and we can import dresses from both sides at the same time, so result is max(abs(L), abs®) L < 0 && R > 0 or L >0 && R < 0: the side with a larger absolute value will import/export its extra dresses from/to current machine or other side, so result is max(abs(L), abs®)

529 Minesweepe

• think carefully B and E

564. Find the Closest Palindrome

647. Palindromic Substrings

• memo valid substring from i to j