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[C++] 纯文本查看 复制代码

#include<bits/stdc++.h>          
using namespace std;
int a[1000000];
int main()
{
	int n;
	cin>>n;
	int mid;
	for (int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	int x;
	cin>>x;
	int l=1;
	int r=n;
	while (1)
	{
		mid=l+(r-l)/2;
		if(a[mid]==x) 
		{
			cout<<mid;
			break;
		}
		else if(x>a[mid]) l=mid+1;
		else if(x<a[mid]) r=mid-1;
		if(l>r) 
		{
			cout<<-1;
			break;
		}
	}
    return 0;
}