1687B - Railway System - CodeForces Solution

#include <bits/stdc++.h>
using namespace std; 
typedef long long int ll;
#define MAXN 300010
const ll MOD = 1e9+7;

ll x[MAXN],y[MAXN],a[MAXN],b[MAXN];
vector<int> adj[20000];
ll n,m,k;


void solve() 
{
    cin >> n >> m;

    vector<pair<int,int>> weights;

    
    for (int i = 0; i < m; i++) {
        vector<char> sV(m, '0');
        sV[i] = '1';
        string s(sV.begin(), sV.end());
        cout << "? "<< s << endl;
        int val;
        cin >> val;
        weights.push_back({val,i});
    }
    sort(weights.begin(), weights.end());

    vector<char> resV(m, '0');

    ll currCost = 0;
    for (int i = 0;i < m; i++) {
        resV[weights[i].second] = '1';
        string s(resV.begin(), resV.end());
        cout << "? " << s << endl;
        int val;
        cin >> val;
        if (val - currCost == weights[i].first) {
            currCost = val;
        } else {
            resV[weights[i].second] = '0';
        }
    }


    cout << "! " <<currCost << endl;




}


int main()
{
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
 
	ll t = 1;
	while (t--) {
        solve();
	}
	return EXIT_SUCCESS;
}