给定有序数组：1，3，6，9，17，31，39，52，61，79，81，90，96，二分查找代码如下：

int binary_search(vector<int>& nums, int target) {
 int left = 0;
 int right = nums.size() - 1;
 while (left <= right) {
  int mid = (left + right) / 2;
  if (nums[mid] == target) {
   return mid;
  } else if (nums[mid] < target) {
   left = mid + 1;
  } else {
   right = mid - 1;
  }
 }
 return -1; // 如果找不到目标元素，返回-1
}