E1. Madhouse (Easy version) （交互题）

题目链接：https://codeforces.com/contest/1287/problem/E1

首先需要知道什么是交互题：https://www.cnblogs.com/mch5201314/p/10875698.html

题意：

想法：

#include <algorithm>
#include <string>
#include <string.h>
#include <vector>
#include <map>
#include <stack>
#include <set>
#include <queue>
#include <math.h>
#include <cstdio>
#include <iomanip>
#include <time.h>
#include <bitset>
#include <cmath>
#include <sstream>
#include <iostream>
#include <cstring>

#define LL long long
#define ls nod<<1
#define rs (nod<<1)+1
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define INF 0x3f3f3f3f

const double eps = 1e-10;
const int maxn = 100 + 10;
const LL mod = 1e9 + 7;

int sgn(double a){return a < -eps ? -1 : a < eps ? 0 : 1;}
using namespace std;

string s;
multiset<string> st;
string ss[maxn];

char ans[maxn*maxn];
bool cmp (string s1,string s2) {
    return s1.size() < s2.size();
}

int buc[maxn*maxn];

int main() {
    int n;
    cin >> n;
    if (n == 1) {
        cout << "? " << 1 << " " << 1 << endl;
        fflush(stdout);
        char c;
        cin >> c;
        cout << "! " << c;
        fflush(stdout);
        return 0;
    }
    cout << "? " << 1 << " " << n << endl;
    fflush(stdout);
    for (int i = 0;i < n*(n+1)/2;i++) {
        cin >> s;
        sort(s.begin(),s.end());
        st.insert(s);
    }
    cout << "? " << 2 << " " << n << endl;
    fflush(stdout);
    for (int i = 0;i < n*(n-1)/2;i++) {
        cin >> s;
        sort(s.begin(),s.end());
        st.erase(st.find(s));
    }
    int cnt = 0;
    for (auto p : st) {
        ss[cnt++] = p;
    }
    sort(ss,ss+cnt,cmp);
    ans[0] = ss[0][0];
    for (int i = 1;i < cnt;i++) {
        for (auto p : ss[i])
            buc[p]++;
        for (auto p : ss[i-1])
            buc[p]--;
        for (int j = 0;j < 127;j++) {
            if (buc[j] > 0) {
                buc[j] = 0;
                ans[i] = j;
                break;
            }
        }
    }
    cout<<"! "<<ans;
    fflush(stdout);
    return 0;
}

参考博客：https://www.luogu.com.cn/blog/Rhodoks/solution-cf1286c1