方法2，满分代码：

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<string>
#define INF 999999999
#define N 1000001
#define MOD 1000000007
#define E 1e-5
using namespace std;
int a[N];
int main()
{
    int n,m;
    int x;
    int left,right,mid;
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>a[i];
    cin>>m;
    while(m--)
    {
        cin>>x;
        left=1;
        right=n;
 
        while(left<right-1)
        {
            mid=(left+right)/2;
            if(a[mid]>x)
                right=mid;
            else
                left=mid;
        }
        if(fabs(a[left]-x)<=fabs(a[right]-x))
            cout<<a[left]<<endl;
        else
            cout<<a[right]<<endl;
    }
    return 0;
}

方法一：

#include <bits/stdc++.h>
using namespace std;

int bsearch_v2(int a[], int n, int key) {
    int left = 0, right = n - 1;
    while (left + 1 < right) {
        int mid = (left + right) / 2;
        if (a[mid] < key)
            left = mid;
        else
            right = mid;
    }
    if (a[left] >= key) return left;
    if (a[right] >= key) return right;
    return n;
}

int main() {
    int n, m;
    cin >> n;
    int a[n];
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    sort(a, a+n);
    cin >> m;
    while (m--) {
        int key;
        cin >> key;
        int ret = bsearch_v2(a, n, key);
        if(ret == n) cout << a[n-1] << endl;
        else if(a[ret] == key) {
            cout << a[ret] << endl;
        } else {
            if(ret == 0) cout << a[0] << endl;
            else if(abs(a[ret-1] - key) <= abs(a[ret] - key))
                cout << a[ret-1] << endl;
            else cout << a[ret] << endl;
        }
    }
    return 0;
}