Set the length of N, block search, each G element, a total of [N / g] group, the block in which the element is located, the average comparison number is [N / g] / 2 times, then check it in block Elements, the average number of comparisons is g / 2 times, and the average lookup number of adds is ([N / g] g) / 2 times.
When the G takes 1/2 times of N, the average lookup number takes a minimum.
Therefore, when n = 2000, g = (20 * Round number 5), about 45, the average lookup number takes a minimum, and the average lookup number is 45 times.
