HDU 3622 bomb game (2-Sat)

HDU 3622 bomb game

Question Link

Ask for a maximum radius so that you can select one of the vertices in each Binary Group.

Train of Thought: Obviously the binary radius, then 2-sat to determine

Code:

#include <cstdio>#include <cstring>#include <cstdlib>#include <vector>#include <cmath>#include <algorithm>using namespace std;const int MAXNODE = 105;struct TwoSet {int n;vector<int> g[MAXNODE * 2];bool mark[MAXNODE * 2];int S[MAXNODE * 2], sn;void init(int tot) {n = tot * 2;for (int i = 0; i < n; i += 2) {g[i].clear();g[i^1].clear();}memset(mark, false, sizeof(mark));}void add_Edge(int u, int uval, int v, int vval) {u = u * 2 + uval;v = v * 2 + vval;g[u^1].push_back(v);g[v^1].push_back(u);}void delete_Edge(int u, int uval, int v, int vval) {u = u * 2 + uval;v = v * 2 + vval;g[u^1].pop_back();g[v^1].pop_back();}bool dfs(int u) {if (mark[u^1]) return false;if (mark[u]) return true;mark[u] = true;S[sn++] = u;for (int i = 0; i < g[u].size(); i++) {int v = g[u][i];if (!dfs(v)) return false;}return true;}bool solve() {for (int i = 0; i < n; i += 2) {if (!mark[i] && !mark[i + 1]) {sn = 0;if (!dfs(i)){for (int j = 0; j < sn; j++)mark[S[j]] = false;sn = 0;if (!dfs(i + 1)) return false;}}}return true;}} gao;const int N = 105;int n;struct Point {double x, y;void read() {scanf("%lf%lf", &x, &y);}} p[N][2];inline double dis(Point a, Point b) {double dx = a.x - b.x;double dy = a.y - b.y;return sqrt(dx * dx + dy * dy);}inline bool xj(Point a, Point b, double r) {if (dis(a, b) > 2 * r) return false;return true;}bool judge(double r) {gao.init(n);for (int i = 0; i < n; i++) {for (int j = i + 1; j < n; j++) {for (int x = 0; x < 2; x++) {for (int y = 0; y < 2; y++) {if (xj(p[i][x], p[j][y], r))gao.add_Edge(i, x, j , y);}}}}return gao.solve();}int main() {while (~scanf("%d", &n)) {for (int i = 0; i < n; i++)for (int j = 0; j < 2; j++)p[i][j].read();double l = 0, r = 1e5;for (int i = 0; i < 30; i++) {double mid = (l + r) / 2;if (judge(mid)) l = mid;else r = mid;}printf("%.2lf\n", l);}return 0;}

HDU 3622 bomb game (2-Sat)