1068 二分查找

#include<bits/stdc++.h>
using namespace std;
int x,a[10000]={0},l,r,mid; 
int main(){
	cin>>x;
	for(int i=1;i<=1500;i++)
	cin>>a[i];
	l=1;r=1500;
		while(l<=r){
			mid=(l+r)/2;
			if(a[mid]==x){cout<<mid;return 0;}
			if(x<a[mid])r=mid-1;
			else l=mid+1;
	}
	cout<<-1;
    return 0;
}