这里要注意的是//向下取整，下次循环时，如果大于查找的数字，start+1。
并且，只能向下取整，如果向上取整。
那么，在比较第一个数时，start = 0 。end = 1。mid = 1。就会进入死循环了。
切记切记。
import math a_list = [2, 5, 23, 45, 67, 89, 90, 123, 234, 345, 567, 7890, 12132] guess_no = 67 answer = -1 start, end = 0, len(a_list) while end - start > 1: mid = (end + start) // 2 print(start, end, mid, a_list[mid]) if a_list[mid] == guess_no: answer = guess_no break elif a_list[mid] < guess_no: start = mid + 1 else: end = mid else: if a_list[start] == guess_no: answer = guess_no print('find it') print(answer) # ==================上面为书，下面为自己================= answer = -1 start, end = 0, len(a_list) while start < end: mid = math.floor((start + end) / 2) print(start, end, mid, a_list[mid]) if guess_no < a_list[mid]: end = mid elif guess_no == a_list[mid]: answer = guess_no break else: start = mid + 1 print(answer) 输出：
0 13 6 90 0 6 3 45 4 6 5 89 find it 67 0 13 6 90 0 6 3 45 4 6 5 89 4 5 4 67 67 Process finished with exit code 0