折半查找法

#include <stdio.h>

int main(void)
{
	int num[8] = {0, 1, 3, 5, 7, 9, 11, 13};
	int key, n;
	int low, high, mid;

	printf("Input the integer to find: ");
	scanf("%d", &key);
	
	for(low=0, high=7; low<=high;)
	{
		mid = (high+low)/2;
		if(key==num[mid])
		{
			printf("Find. %d's position is %d\n", key, mid+1);
			break;
		}
		else if(key > num[mid])
			low = mid+1; //当时我自己写的是low=mid和high=mid，后来终于明白了不能这样写，这样写会使low永远无法大于high
		else
			high = mid-1;
	}
	if(low>high)
		printf("Not find.\n");

	system("pause"); /*为了在visual studio 类的编译器中能暂停一下，不让就一闪而过了*/

	return 0;
}

#include <stdio.h>
int main()
{
	int s[10]={0,1,2,3,4,5,6,7,8,9};
	int key,left=0,right=9,mid, i; /*key是存放需要查找的数的,当然你可以随便改为别的*/

	scanf("%d", &key);

	while(left<=right)
	{
		mid=(left+right)/2;
		if(key==s[mid]) 
		{
			printf("Find. %d's position is %d\n", key, mid);
			break;
		}
		else if(key>s[mid]) 
			left=mid+1;
		else 
			right=mid-1;
	}
	if(left>right)
		printf("Not find.\n");
	system("pause"); /*为了在visual studio 类的编译器中能暂停一下，不让就一闪而过了*/
	return 0;
}