AtCoder Beginner Contest 268 D Unique Usernamed

Unique Username

模拟 搜索

全排列模拟，直接搜索

#include <iostream>
#include <cstdio>
#include <map>
#include <string>
using namespace std;
const int maxn = 20;
map<string, int>mp;
string s[maxn];
int vis[maxn];
string ans = "";
int _maxx = 0, n, m;

void dfs(int now, int _, string snow)
{
    if(now == n)
    {
        if(snow.size() >= 3 && mp.count(snow) == 0)
            ans = snow;
        return;
    }
    if(now == 0)
    {
        for(int i=0; i<n && ans.size() == 0; i++)
        {
            if(vis[i]) continue;
            vis[i] = 1;
            dfs(now + 1, _, snow + s[i]);
            vis[i] = 0;
        }
        return;
    }
    for(int i=1; _maxx - _ - i >= n - 1 - now && ans.size() == 0; i++)
    {
        snow += "_";
        for(int j=0; j<n && ans.size() == 0; j++)
        {
            if(vis[j]) continue;
            vis[j] = 1;
            dfs(now + 1, _ + i, snow + s[j]);
            vis[j] = 0;
        }
    }
}

int main()
{
    cin >> n >> m;
    int sum = 0;
    for(int i=0; i<n; i++)
    {
        cin >> s[i];
        sum += s[i].size();
    }
    _maxx = 16 - sum;
    for(int i=0; i<m; i++)
    {
        string a;
        cin >> a;
        mp[a] = 1;
    }
    dfs(0, 0, "");
    if(ans.size() == 0) ans = "-1";
    cout << ans << endl;
    return 0;
}