acm.sgu.ru/369

acm.sgu.ru/369.cc

@@ -0,0 +1,95 @@
+#include <cstdio>
+#include <vector>
+#include <map>
+#include <iostream>
+#include <algorithm>
+using namespace std;
+
+struct UnionFind {
+    vector<int> p, sz;
+
+    UnionFind(int n) : p(n), sz(n, 1) {
+        for (int i = 0; i < n; i++)
+            p[i] = i;
+    }
+
+    int Find(int x) {
+        return p[x] == x ? x : (p[x] = Find(p[x]));
+    }
+
+    void Union(int x, int y) {
+        x = Find(x);
+        y = Find(y);
+        if (x != y) {
+            if (sz[x] > sz[y]) swap(x, y);
+            p[x] = y;
+            sz[y] += sz[x];
+        }
+    }
+
+    int Size(int x) {
+        return sz[Find(x)];
+    }
+};
+
+void relabel(vector<int> &v) {
+    int n = v.size();
+
+    vector<int> s(v);
+    sort(s.begin(), s.end());
+
+    map<int, int> mp;
+    for (int i = 0; i < n; i++)
+        mp[s[i]] = i;
+
+    for (int i = 0; i < n; i++)
+        v[i] = mp[v[i]];
+}
+
+int main()
+{
+    int N;
+    scanf("%d", &N);
+
+    vector<int> x(N), y(N);
+    for (int i = 0; i < N; i++)
+        scanf("%d %d", &x[i], &y[i]);
+
+    relabel(x);
+    relabel(y);
+
+    UnionFind uf(N+10);
+
+    vector<pair<int, int> > v(N);
+    for (int i = 0; i < N; i++) {
+        v[i].first = x[i];
+        v[i].second = y[i];
+    }
+    sort(v.begin(), v.end());
+
+    for (int i = 1; i < N; i++) {
+        if (v[i-1].first == v[i].first) {  // same x
+            uf.Union(v[i-1].second, v[i].second);
+        }
+    }
+
+    long long ans = 0;
+
+    int i, j;
+    for (i = 0; i < N; i = j) {
+        for (j = i + 1; j < N && v[i].first == v[j].first; j++);
+        // [i, j) has same x
+
+        vector<int> w;
+        for (int k = i; k < j; k++)
+            w.push_back(uf.Find(v[k].second));
+
+        sort(w.begin(), w.end());
+        w.erase(unique(w.begin(), w.end()), w.end());
+
+        for (int k = 0; k < (int)w.size(); k++)
+            ans += uf.Size(w[k]);
+    }
+
+    cout << ans << endl;
+}