def binarySearchRecursion(ls, target, left, right):
if(target < ls[left]) or (target > ls[right]):
return "没有找到"
else:
#python 整除符号 // 可以理解为表示向下取整 例如:7//2 = 3
mid = (left + right)//2
#递归的三分支 如果相等则直接返回;如果大于...;如果小于...
if (target == ls[mid]):
return mid
elif target > ls[mid]:
return binarySearchRecursion(ls, target, mid+1, right)
else:
return binarySearchRecursion(ls, target, left, mid-1)