File size: 4,327 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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 | #include <bits/stdc++.h>
using namespace std;
const int MAX_Q = 50000;
long long query_count = 0;
int n;
long long k;
long long do_query(int x, int y) {
++query_count;
cout << "QUERY " << x << " " << y << '\n';
cout.flush();
long long v;
if (!(cin >> v)) exit(0); // in interactive environment, this should not happen
return v;
}
void done(long long ans) {
cout << "DONE " << ans << '\n';
cout.flush();
}
void solveBFS(long long kk) {
struct Node {
long long val;
int x, y;
};
struct Cmp {
bool operator()(const Node &a, const Node &b) const {
return a.val > b.val;
}
};
priority_queue<Node, vector<Node>, Cmp> pq;
vector<vector<char>> vis(n + 2, vector<char>(n + 2, 0));
long long v = do_query(1, 1);
vis[1][1] = 1;
pq.push({v, 1, 1});
long long popped = 0;
long long ans = -1;
while (!pq.empty()) {
Node cur = pq.top(); pq.pop();
++popped;
if (popped == kk) {
ans = cur.val;
break;
}
int x = cur.x, y = cur.y;
if (x + 1 <= n && !vis[x + 1][y]) {
long long nv = do_query(x + 1, y);
vis[x + 1][y] = 1;
pq.push({nv, x + 1, y});
}
if (y + 1 <= n && !vis[x][y + 1]) {
long long nv = do_query(x, y + 1);
vis[x][y + 1] = 1;
pq.push({nv, x, y + 1});
}
}
if (ans == -1 && !pq.empty()) ans = pq.top().val; // fallback, should not happen
done(ans);
}
void solveRowMerge(long long kk) {
struct Node {
long long val;
int row, col;
};
struct Cmp {
bool operator()(const Node &a, const Node &b) const {
return a.val > b.val;
}
};
priority_queue<Node, vector<Node>, Cmp> pq;
for (int i = 1; i <= n; ++i) {
long long v = do_query(i, 1);
pq.push({v, i, 1});
}
long long popped = 0;
long long ans = -1;
while (!pq.empty()) {
Node cur = pq.top(); pq.pop();
++popped;
if (popped == kk) {
ans = cur.val;
break;
}
int i = cur.row, j = cur.col;
if (j < n) {
long long nv = do_query(i, j + 1);
pq.push({nv, i, j + 1});
}
}
if (ans == -1 && !pq.empty()) ans = pq.top().val; // fallback, should not happen
done(ans);
}
void solveFallback(long long kk) {
struct Node {
long long val;
int row, col;
};
struct Cmp {
bool operator()(const Node &a, const Node &b) const {
return a.val > b.val;
}
};
priority_queue<Node, vector<Node>, Cmp> pq;
for (int i = 1; i <= n; ++i) {
long long v = do_query(i, 1);
pq.push({v, i, 1});
}
long long popped = 0;
long long ans = -1;
while (!pq.empty()) {
Node cur = pq.top(); pq.pop();
++popped;
ans = cur.val;
if (popped == kk) break;
int i = cur.row, j = cur.col;
if (j < n) {
if (query_count + 1 > MAX_Q) {
// cannot query more, so stop adding new elements
continue;
}
long long nv = do_query(i, j + 1);
pq.push({nv, i, j + 1});
}
}
done(ans);
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
if (!(cin >> n >> k)) return 0;
long long totcells = 1LL * n * n;
if (totcells <= 0) {
done(0);
return 0;
}
if (k < 1) k = 1;
if (k > totcells) k = totcells;
if (k == 1) {
long long val = do_query(1, 1); // smallest element
done(val);
return 0;
}
if (k == totcells) {
long long val = do_query(n, n); // largest element
done(val);
return 0;
}
long long costBFS = 2 * k - 1; // 1 + 2*(k-1)
long long costMerge = n + k - 1; // n initial + k-1 next
bool canBFS = (costBFS <= MAX_Q);
bool canMerge = (costMerge <= MAX_Q);
if (canBFS && (!canMerge || costBFS <= costMerge)) {
solveBFS(k);
} else if (canMerge) {
solveRowMerge(k);
} else {
// Both exceed limit in worst-case; use limited merge heuristic
solveFallback(k);
}
return 0;
} |