1: Quite simple question, calendar related calculation. 2: Something close to binary search, find the missing number from consecutive integers. e.g., 0, 1, 2, 4, 5, should return 3. A little tricky for boundary conditions. Another simple question but cannot remember. 3: Double linked list insert and delete, with some special conditions. Simple. Another OOD question. 4: Something like leetcode jump game. But the jump length depends on the last jump made. For example, in step N, the man jumped M, the next step he can jump M-1, M or M+1.