update

poj/2560.freckles/main.cc

@@ -0,0 +1,83 @@
+#include <cmath>
+#include <cstdio>
+#include <cstring>
+#include <queue>
+
+using namespace std;
+
+const int N = 200;
+
+struct UF {
+  int id[N];
+  int sz[N];
+  int cnt;
+} uf;
+
+int find(int i) {
+  if (i == uf.id[i]) return i;
+  int j = find(uf.id[i]);
+  uf.id[i] = j;
+  return j;
+}
+
+bool is_join(int i, int j) { return find(i) == find(j); }
+
+void join(int i, int j) {
+  i = find(i);
+  j = find(j);
+  if (i == j) return;
+  if (uf.sz[i] < uf.sz[j]) {
+    uf.id[i] = j;
+  } else {
+    if (uf.sz[i] == uf.sz[j]) uf.sz[i]++;
+    uf.id[j] = i;
+  }
+  uf.cnt--;
+}
+
+struct V {
+  double x;
+  double y;
+  double operator-(const V &that) const {
+    double dx = this->x - that.x;
+    double dy = this->y - that.y;
+    return sqrt(dx * dx + dy * dy);
+  }
+} v[N];
+
+struct E {
+  int v1;
+  int v2;
+  double len;
+  E(int v1, int v2, double len) : v1(v1), v2(v2), len(len) {}
+  bool operator<(const E &that) const {
+    return this->len > that.len;
+  }
+};
+
+int main() {
+  int n, e;
+  scanf("%d", &n);
+  for (int i = 0; i < n; i++)
+    scanf("%lf %lf", &v[i].x, &v[i].y);
+  priority_queue<E> q;
+  for (int i = 0; i < n - 1; i++) {
+    for (int j = i + 1; j < n; j++) {
+      q.push(E(i, j, v[i] - v[j]));
+      e++;
+    }
+  }
+  for (int i = 0; i < n; i++) uf.id[i] = i;
+  memset(uf.sz, 0, sizeof(uf.sz));
+  uf.cnt = n;
+  double len = 0.;
+  while (uf.cnt != 1) {
+    E edge = q.top();
+    q.pop();
+    if (is_join(edge.v1, edge.v2)) continue;
+    join(edge.v1, edge.v2);
+    len += edge.len;
+  }
+  printf("%.2lf\n", len);
+  return 0;
+}