折半查找
折半查找的前提是有序的,与中间值进行比较,如果有序的则返回;否则,改变始末位置,再进行查找
实现方法:1 循环实现 2 递归实现
1 循环实现
#include<stdio.h>
int binary_search(int *array,int n,int data);
int main()
{
int array[10]={
1,2,3,4,5,6,7,8,9,10
};
printf("please input the number that you want search\n");
int num;
scanf("%d",&num);
int result=binary_search(array,10,num);
if(result==-1)
{
printf("not found %d\n",num);
}
else
printf("the index is %d\n",result);
}
int binary_search(int *array,int n,int data)
{
int start,end,mid;
start=0;
end=n-1;
while(start<=end)
{
mid=(start+end)/2;
if(array[mid]==data)
{
return mid;
}
else if(array[mid]>data)
{
end=mid-1;
}
else
{
start=mid+1;
}
}
return -1;
}
2 递归实现
int binary_search2(int *array,int start,int end ,int value)
{ if(start>end) return -1;
int mid=(start+end)/2;
if(array[mid]==value)
{
return mid;
}
else if(array[mid]>value)
{
binary_search2(array,start,mid-1,value);
}
else
binary_search2(array,mid+1,end,value);
}