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OI-codes/Codeforces/1697/D/D.cpp

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#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
using std::cin;
using std::cout;
using std::endl;
const int N = 1e4 + 5;
int n, a[N], b[N], lst[N];
int query1(int x) {
char res;
cout << "? 1 " << x << endl;
cin >> res;
return res - 'a' + 1;
}
int query2(int l, int r) {
int res;
cout << "? 2 " << l << ' ' << r << endl;
cin >> res;
return res;
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
lst[a[1] = query1(1)] = 1;
for (int i = 2; i <= n; i++) {
int cnt = 0;
for (int j = 1; j <= 26; j++) {
if (lst[j]) b[++cnt] = lst[j];
}
std::sort(b + 1, b + 1 + cnt);
int l = 1, r = cnt, res = 0;
while (l <= r) {
int mid = l + r >> 1;
if (query2(b[mid], i) == cnt - mid + 1) {
res = mid;
l = mid + 1;
} else {
r = mid - 1;
}
}
lst[a[i] = res ? a[b[res]] : query1(i)] = i;
}
cout << "! ";
for (int i = 1; i <= n; i++) {
cout << char(a[i] - 1 + 'a');
}
cout << endl;
return 0;
}