Time complexity calculation rules :
①Basic operation, consider its time complexity to be O(1) # Addition, subtraction, multiplication and division and other similar operations
②Sequential structure, time complexity is calculated by addition
③Circular structure, time complexity is calculated by multiplication
④Branch structure, maximum time complexity
⑤When judging the efficiency of an algorithm, it is often only necessary to pay attention to the highest order item of the number of operations , and other minor items and constant items can be ignored
⑥In the absence of special instructions, the time complexity of the algorithms we analyzed refers to the worst time complexity
