C语言实现二分查找（普通实现+递归实现）

二分查找主要过程：

#include<stdio.h>
#include<stdlib.h>

typedef struct List
{
	int* data;
	int length;
	int size;
}List;

List* initList(int length)
{
	List* list = (List*)malloc(sizeof(List));
	list->data = (int*)malloc(sizeof(int) * length);
	list->length = length;
	list->size = 0;

	return list;
}

void listAdd(List* list, int data)
{
	list->data[list->size] = data;
	list->size++;
}

void PrintList(List* list)
{
	for (int i = 0; i < list->size; i++)
	{
		printf("%d ", list->data[i]);
	}
	printf("
");
}

int BinarySearch(int key, List* list)
{
	int start = 0;
	int end = list->size - 1;
	int mid;

	while (start <= end)
	{
		mid = (start + end) / 2;
		if (list->data[mid] == key)
		{
			return mid;
		}

		else if (list->data[mid] > key)
		{
			end = mid - 1;
		}

		else
		{
			start = mid + 1;
		}
	}
	return -1;
}

int BinarySearchRecursion(List* list, int key,int start,int end)
{
	int mid = (start + end) / 2;

	if (start == end && list->data[start] != key)
	{
		return -1;
	}

	//if (start == end)
	//{
	//	if (list->data[start] == key)
	//	{
	//		return start;
	//	}
	//	else
	//	{
	//		return -1;
	//	}
	//}

	if (list->data[mid] == key)
	{
		return mid;
	}

	else if (list->data[mid] < key)
	{
		return BinarySearchRecursion(list, key, mid + 1, end);
	}

	else
	{
		return BinarySearchRecursion(list, key, start, mid - 1);
	}
}

int main()
{
	List* list = initList(9);

	for (int i = 1; i <=9; i++)
	{
		listAdd(list, i);
	}

	PrintList(list);

	/*int ret =  BinarySearch(5,list);
	printf("%d ", ret);*/
	printf("data %d in %d
",7, BinarySearch(7, list));
	printf("data %d in %d
",10, BinarySearch(10, list));
	printf("data %d in %d
",1, BinarySearch(1, list));
	printf("data %d in %d
",3, BinarySearch(3, list));

	printf("data %d in %d
", 7, BinarySearchRecursion(list,7,0,9));
	printf("data %d in %d
", 10, BinarySearchRecursion(list, 10, 0, 9));
	printf("data %d in %d
", 1, BinarySearchRecursion(list, 1, 0, 9));
	printf("data %d in %d
", 3, BinarySearchRecursion(list, 3, 0, 9));

	system("pause");
	return 0;
}

测试结果：

数组实现版：

#include<stdio.h>
#include<stdlib.h>

int Search(int arr[],int length, int key)
{
	int mid = (length - 1 + 0) / 2;
	int start = 0;
	int end = length - 1;
	while (start <= end )
	{
		mid = (start + end) / 2;
		if (arr[mid] == key)
		{
			return mid;
		}

		else if(arr[mid]<key)
		{
			start = mid+1;
		}
		
		else
		{
			end = mid-1;
		}
	}
	return -1;
}

int main()
{
	int arr[10] = { 1,2,3,4,5,6,7,8,9,10};
	int ret = Search(arr, 10, 6);

	printf("%d ", ret);
	system("pause");
	return 0;
}

测试结果：