题解

二分查找

#include<iostream>
using namespace std;
int a[1000],m,n,l=1,r=1000000,ans=0,mid;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i];
    cin>>m;r=n;
    while(l<=r){
        mid=(l+r)/2;
        if(a[mid]>=m){ans=mid;r=mid-1;}
        else{l=mid+1;}
    }
    if(a[ans]==m)cout<<ans;
    else cout<<-1; 
    return 0;
}