This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
// Hallelujah, praise the one who set me free
// Hallelujah, death has lost its grip on me
// You have broken every chain, There's salvation in your name
// Jesus Christ, my living hope
#include <bits/stdc++.h>
using namespace std;
#define REP(i, s, e) for (int i = (s); i < (e); i++)
#define RREP(i, s, e) for (int i = (s); i >= (e); i--)
template <class T>
inline bool mnto(T& a, T b) {return a > b ? a = b, 1 : 0;}
template <class T>
inline bool mxto(T& a, T b) {return a < b ? a = b, 1: 0;}
typedef long long ll;
typedef long double ld;
#define FI first
#define SE second
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
typedef tuple<int, int, int> iii;
#define ALL(_a) _a.begin(), _a.end()
#define SZ(_a) (int) _a.size()
#define pb push_back
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;
typedef vector<iii> viii;
#ifndef DEBUG
#define cerr if (0) cerr
#endif
const int INF = 1000000005;
const ll LINF = 1000000000000000005ll;
ll n;
vll qry;
inline bool ask(ll x) {
cout << "? " << x << endl;
bool r; cin >> r;
return r;
}
int main() {
cin >> n;
ll lo = 1, hi = n, mid;
while (lo < hi) {
mid = lo + hi + 1 >> 1;
cerr << ' ' << mid << '\n';
qry.pb(mid);
lo = mid;
}
qry.pop_back();
ll lft = LINF, rht = -LINF;
ll d = 0;
REP (i, 0, SZ(qry)) {
if (i & 1 ^ 1) {
d -= qry[i];
} else {
d += qry[i];
}
mnto(lft, d);
mxto(rht, d);
}
ll s = -lft + 1;
assert(s + rht <= n);
ask(s);
lo = 1, hi = n;
bool tog = 0;
while (lo < hi) {
mid = lo + hi + 1 >> 1;
if (!tog) {
s -= mid;
} else {
s += mid;
}
tog ^= 1;
if (s < 1 || s > n) {
break;
}
int res = ask(s);
if (res) {
lo = mid;
} else {
hi = mid - 1;
}
}
assert(hi - lo <= 2);
if (hi - lo == 2) {
assert(hi == n);
ask(1);
if (ask(n)) {
hi = n - 1;
} else {
hi = n;
}
}
cout << "= " << hi << '\n';
return 0;
}
Compilation message (stderr)
Colors.cpp: In function 'int main()':
Colors.cpp:50:23: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
50 | mid = lo + hi + 1 >> 1;
| ~~~~~~~~^~~
Colors.cpp:59:15: warning: suggest parentheses around arithmetic in operand of '^' [-Wparentheses]
59 | if (i & 1 ^ 1) {
| ~~^~~
Colors.cpp:73:23: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
73 | mid = lo + hi + 1 >> 1;
| ~~~~~~~~^~~
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