C language _ search algorithm _ binary search method (binary search method)

Binary search method (binary search method)

• Basic principle
  Divide n elements in half from the middle, take the middle number mid=a[0+n-1]/2 and compare it with the number x you want to find .
  If mid=x , X is found and the algorithm terminates.
  If mid>x , we only need to continue searching for X in the left half of the array a (a[(0+N-1)/2-1]~a[N-1]).
  If mid>x , we only need to continue searching for X in the left half of the array a (a[0]~a[(0+N-1)/2-1]).

The specific code is as follows:

//二分查找法（折半查找法）
#include<stdio.h>
#define N 10
int main()
{
    
    
 int x,mid,top,bottom;
 int a[N]={
    
    2,3,5,7,8,11,14,35,68,70};
 printf("请输入要查找的数：");
 scanf("%d",&x);
 bottom=0;  top=N-1;  //查找区域初始化（在a[bottom]~a[top]内查找） 
 while(bottom<=top)  //注意！！！  此处是 <= 而不是 < 。
 {
    
    
  mid=(top+bottom)/2;
  if(x<a[mid])
  top=mid-1;
  else if(x>a[mid])
  bottom=mid+1;
  else break;         //如果等于中间位置的数据，则找到，结束查找。 
 }
 if(bottom<=top)              //找到 
 printf("%d在数组中的下标为%d\n",x,mid);
 else
 printf("查无此数");          //未找到 
 return 0; 
 }