Day9

 3.代码示例

#include<iostream>
using namespace std;
int main(){
    int a[10]={2,3,4,5,6,7,8,9,12,18};
    int i;
    for(i=0;i<10;i++){
        cout<<a[i]<<" ";
    }
    cout<<endl;
    int x,l,r,mid;
    cin>>x;
    l=0;r=10;
    while(l<=r){
        mid=(l+r)/2;
        if(x<a[mid]){
            r=mid-1;
        }
        else if(x>a[mid]){
            l=mid+1;
        }
        else{
        cout<<"下标值为："<<mid+1;
        break;
    }
    }
    if(a[mid]!=x)
    cout<<"Not be found";
    return 0;
} 

4.结果输出