int getNumberSameAsIndex(int* nums, int numsSize) {
int a=numsSize-1; //二分法查找
int b=0;
while(b<=a)
{
int mid=b+(a-b)/2;
if(nums[mid]==mid)
return mid;
else if(nums[mid]>mid)
a=mid-1;
else
b=mid+1;
}
return -1;
}