C语言折半查找法

 

#include<stdio.h>

int find(int x,int y[],int n);

int main(void)

{

       int A[]={1,2,3,4,5,6,9};

       int b=12;

       int f;

       f=find(b,A,c);

       if(f==-1)

              printf("Can not find element b in arry A[]\n");

       else

              printf("Find element b in arry A[]:the %dth element\n",f);

       return 0;

}

 

//折半查找法，用代查元素的个数与有序数组的中间元素进行比较，

//若是大于中间的元素，则在后一半继续查找，否则在前一半进行查找

int find(int x,int y[],int n)

{

       int mid;

       int low=0;

       int high=n-1;

       while(low<=high)

       {

              mid=(low+high)/2;

              if(x<y[mid])

                     high=mid-1;

              else if(x>y[mid])

                     low=mid+1;

              else

                     return mid+1;

       }

       return -1;

}