二分查找模板

二分查找，找不到时返回-1
//二分查找
int binarySearch(int arr[], int len, int key)
{
int left = 0;
int right = len - 1;
int mid;

while (left <= right) {
mid = (left + right) / 2;
if (key < arr[mid]) {//key在左边
right = mid - 1;
} else if (arr[mid] < key) {//key在右边
left = mid + 1;
} else {
return mid;
}
}
return -1;
}