HDU 5046 Airport (repeated DLX coverage), hdudlx

HDU 5046 Airport (repeated DLX coverage), hdudlx
HDU 5046 Airport

Question Link

For some airports, K airports must be selected to minimize the maximum number of airports from other airports.

Train of Thought: Dual + DLX repeated coverage to determine

Code:

#include <cstdio>#include <cstring>using namespace std;const int MAXNODE = 4005;const int MAXM = 65;const int MAXN = 65;const int INF = 0x3f3f3f3f;int K;struct DLX {int n, m, size;int U[MAXNODE], D[MAXNODE], R[MAXNODE], L[MAXNODE], row[MAXNODE], col[MAXNODE];int H[MAXN], S[MAXM];int ansd, ans[MAXN];void init(int n, int m) {this->n = n;this->m = m;ansd = INF;for(int i = 0; i <= m; i++) {S[i] = 0;U[i] = D[i] = i;L[i] = i - 1;R[i] = i + 1;}R[m] = 0; L[0] = m; size = m;for(int i = 1; i <= n; i++)H[i] = -1;}void Link(int r, int c) {++S[col[++size] = c];row[size] = r;D[size] = D[c];U[D[c]] = size;U[size] = c;D[c] = size;if(H[r] < 0) H[r] = L[size] = R[size] = size;else {R[size] = R[H[r]];L[R[H[r]]] = size;L[size] = H[r];R[H[r]] = size;}}void remove(int c) {for(int i = D[c]; i != c; i = D[i]) {L[R[i]] = L[i];R[L[i]] = R[i];}}void resume(int c) {for(int i = U[c]; i != c; i = U[i])L[R[i]] = R[L[i]] = i;}bool v[MAXNODE];int f() {int ret = 0;for(int c = R[0]; c != 0; c = R[c]) v[c] = true;for(int c = R[0]; c != 0; c = R[c]) {if(v[c]) {ret++;v[c] = false;for(int i = D[c]; i != c; i = D[i])for(int j = R[i]; j != i; j = R[j])v[col[j]] = false;}}return ret;}bool Dance(int d) {if(d + f() > K) return false;if(R[0] == 0) {return d <= K;}int c = R[0];for(int i = R[0]; i != 0; i = R[i]) {if(S[i] < S[c])c = i;}for(int i = D[c]; i != c; i = D[i]) {remove(i);for(int j = R[i]; j != i; j = R[j]) remove(j);ans[d] = row[i];if (Dance(d + 1)) return true;for(int j = L[i]; j != i; j = L[j]) resume(j);resume(i);}return false;}} gao;typedef long long ll;int T, n;const int N = 65;struct City {ll x, y;void read() {scanf("%I64d%I64d", &x, &y);}} c[N];ll dis(City a, City b) {ll dx = a.x - b.x; if (dx < 0) dx = -dx;ll dy = a.y - b.y; if (dy < 0) dy = -dy;return dx + dy;}int main() {int cas = 0;scanf("%d", &T);while (T--) {scanf("%d%d", &n, &K);for (int i = 1; i <= n; i++) c[i].read();ll l = 0, r = 100000000000LL;while (l < r) {ll mid = (l + r) / 2;gao.init(n, n);for (int i = 1; i <= n; i++) {for (int j = 1; j <= n; j++) {if (dis(c[i], c[j]) <= mid)gao.Link(i, j);}}if (gao.Dance(0)) r = mid;else l = mid + 1;}printf("Case #%d: %I64d\n", ++cas, l);}return 0;}