File size: 4,372 Bytes
1fd0050 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 | #include <bits/stdc++.h>
using namespace std;
static const int QUERY_LIMIT = 50000;
struct Node {
long long v;
int x, y;
};
struct CmpMin {
bool operator()(const Node& a, const Node& b) const { return a.v > b.v; }
};
struct CmpMax {
bool operator()(const Node& a, const Node& b) const { return a.v < b.v; }
};
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
long long k;
if (!(cin >> n >> k)) return 0;
const long long total = 1LL * n * n;
const int N1 = n + 1;
const int SZ = N1 * N1;
vector<long long> cacheVal(SZ);
vector<unsigned char> known(SZ, 0);
vector<int> vis(SZ, 0);
int visToken = 0;
int used = 0;
auto idx = [&](int x, int y) -> int { return x * N1 + y; };
auto query = [&](int x, int y) -> long long {
int p = idx(x, y);
if (known[p]) return cacheVal[p];
if (used >= QUERY_LIMIT) {
// Out of budget; output something and exit gracefully.
cout << "DONE " << 0 << "\n";
cout.flush();
exit(0);
}
cout << "QUERY " << x << " " << y << "\n";
cout.flush();
long long v;
if (!(cin >> v)) exit(0);
used++;
known[p] = 1;
cacheVal[p] = v;
return v;
};
auto kthSmallestHeap = [&](long long t) -> long long {
++visToken;
priority_queue<Node, vector<Node>, CmpMin> pq;
vis[idx(1, 1)] = visToken;
pq.push({query(1, 1), 1, 1});
while (!pq.empty()) {
Node cur = pq.top();
pq.pop();
if (--t == 0) return cur.v;
if (cur.x < n) {
int nx = cur.x + 1, ny = cur.y;
int p = idx(nx, ny);
if (vis[p] != visToken) {
vis[p] = visToken;
pq.push({query(nx, ny), nx, ny});
}
}
if (cur.y < n) {
int nx = cur.x, ny = cur.y + 1;
int p = idx(nx, ny);
if (vis[p] != visToken) {
vis[p] = visToken;
pq.push({query(nx, ny), nx, ny});
}
}
}
return 0;
};
auto kthLargestHeap = [&](long long t) -> long long {
++visToken;
priority_queue<Node, vector<Node>, CmpMax> pq;
vis[idx(n, n)] = visToken;
pq.push({query(n, n), n, n});
while (!pq.empty()) {
Node cur = pq.top();
pq.pop();
if (--t == 0) return cur.v;
if (cur.x > 1) {
int nx = cur.x - 1, ny = cur.y;
int p = idx(nx, ny);
if (vis[p] != visToken) {
vis[p] = visToken;
pq.push({query(nx, ny), nx, ny});
}
}
if (cur.y > 1) {
int nx = cur.x, ny = cur.y - 1;
int p = idx(nx, ny);
if (vis[p] != visToken) {
vis[p] = visToken;
pq.push({query(nx, ny), nx, ny});
}
}
}
return 0;
};
long long ans = 0;
if (total <= QUERY_LIMIT) {
vector<long long> vals;
vals.reserve((size_t)total);
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
vals.push_back(query(i, j));
}
}
nth_element(vals.begin(), vals.begin() + (k - 1), vals.end());
ans = vals[(size_t)(k - 1)];
} else {
long long tSmall = k;
long long tLarge = total - k + 1;
long long t = min(tSmall, tLarge);
if (t <= QUERY_LIMIT) {
if (tSmall <= tLarge) ans = kthSmallestHeap(tSmall);
else ans = kthLargestHeap(tLarge);
} else {
// No known exact strategy within budget for arbitrary k when total > QUERY_LIMIT.
// Best-effort: fall back to heap from closer end (still will exceed limit if t > QUERY_LIMIT).
if (tSmall <= tLarge) ans = kthSmallestHeap(tSmall);
else ans = kthLargestHeap(tLarge);
}
}
cout << "DONE " << ans << "\n";
cout.flush();
// Interactor may print a score; try to read and exit.
double score;
if (cin >> score) { /* ignore */ }
return 0;
} |