常用算法集合

二分查找

int binary_search(const int arr[], int start, int end, int key){
	int res = -1;
	int mid;
	while(start <= end){
		mid = begin + (end - begin) / 2;
		if(arr[mid] == key){
			res = mid;
			return res;
		}
		else if(arr[mid] < key)
				start = mid + 1;
		else if(arr[mid] > key)
				end = mid - 1;
			
	}
	return res; //单一出口
}