找出数组中某个元素第一次出现的位置

Given a sorted array, write a function to search first occurrence of a number in the array. If not found return -1.
Example::
{2,2,2,3,4,5,5,6,6,8,9}
search 6

should return 7.

给定一个排序的数组，找出数组中某个元素第一次出现的位置。如果没有找到返回-1.

int find_first_elem(int arr[],int low,int high,int elem){if (low>high){return -1;}int mid = low + (high-low)/2;if (arr[mid] == elem){int index = find_first_elem(arr,low,mid-1,elem);return (index == -1?mid:index);//表示mid之前没有elem 返回mid 否则index}elseif (arr[mid]>elem){find_first_elem(arr,low,mid-1,elem);}elsefind_first_elem(arr,mid+1,high,elem);}