70pts

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+10;
pair<int,int> b[]={{0,6},{1,2},{2,5},{4,4},{6,6},{7,3},{8,7}};
int cnt,x;
int ans[N],idx;
bool dfs(int u,int sum)
{
	if(!u) //走到第一位了
	{
		if(sum==x) //刚好用完
		{
			for(int i=0;i<idx;i++)
			{
				cout<<ans[i];
			}
			cout<<endl;
			return true;
		}
		else return false;
	}
	if(sum+u*7<x) return false; //如果剩余的全部选8都不够
	for(int i=0;i<7;i++)
	{
		if(u==cnt&&i==0) continue;//如果是第一位数字不能选0
		ans[idx++]=b[i].first;
		if(dfs(u-1,sum+b[i].second)) return true;
		else idx--;
	}
}
int main()
{
	int T;
	cin>>T;
	while(T--)
	{
		idx=0;
		cin>>x;
		cnt=(x+6)/7;//计算最多位数
		if(!dfs(cnt,0)) cout<<-1<<endl;
	}
	return 0;
}

100pts

#include <iostream>
#include <algorithm>
using namespace std;

int a[7] = {8, -1, 1, 7, 4, 2, 6};

int main()
{
    int t;
    cin >> t;
    while (t--)
    {
        int n;
        cin >> n;
        int x = n % 7;
        if (n <= 7)
        {
            cout << a[x] << endl;
            continue;
        }
        string ans = "";
        if (x == 0)
        {
            for (int i = 0; i < n / 7; i++) ans += "8";
        }
        else if (x == 1)
        {
            ans += "10";
            for (int i = 0; i < n / 7 - 1; i++) ans += "8";
        }
        else if (x == 2)
        {
            ans += "18";
            for (int i = 0; i < n / 7 - 1; i++) ans += "8";
        }
        else if (x == 3)
        {
            if (n / 7 == 1) ans = "22";
            else
            {
                ans += "200";
                for (int i = 0; i < n / 7 - 2; i++) ans += "8";
            }
        }
        else if (x == 4)
        {
            ans += "20";
            for (int i = 0; i < n / 7 - 1; i++) ans += "8";
        }
        else if (x == 5)
        {
            ans += "28";
            for (int i = 0; i < n / 7 - 1; i++) ans += "8";
        }
        else if (x == 6)
        {
            ans += "68";
            for (int i = 0; i < n / 7 - 1; i++) ans += "8";
        }
        cout << ans << endl;
    }
}