这段代码怎样写成递归的啊

Question

int fun(int a[], int length, int result) {
int first = 0, last = length - 1;
int middle = 0;
while (first <= last) {
middle = (first + last) >> 1;
if (a[middle] == result) {
return middle;
} else if (a[middle] > result) {
last = middle - 1;
} else {
first = middle + 1;
}
}
return -1;
}
这段代码什么意思呢

Answer 1

 :     右移运算符，num >> 1,相当于num除以2

这段代码是在长度为length的数组a[]中寻找数字result所在的位置，如未找到返回-1；

例: a[]={3,6,7,9,12,5}; length=6; rusult=7
return 3