一、二分法基本功
1、通用二分模板,二分T(n)= log2n
伪码:异常检查;start + 1 < end ;start + (end - start) / 2 ;A[mid] ==, <, >; A[start] A[end] ? target
start= 0, end = length - 1 while (start + 1 < end) {//1、循环条件相邻就退出 mid = start + (end - start) // 2、mid的取值不会越界 if [mid] == target {return mid or 赋值} else if [mid] <target {start = mid} else [mid] > target{end = mid} } //3、端点检测 if [start] ,[end]?= target {return start or end} return - 1