Adding submissions

kattis/The 2014 Nordic Collegiate Programming Contest/G.cpp

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+// https://ncpc14.kattis.com/problems/outing
+
+#include<bits/stdc++.h>
+using namespace std;
+#define __ ios_base::sync_with_stdio(0); cin.tie(0);
+#define endl '\n'
+#define foreach(it, x) for (__typeof (x).begin() it = (x).begin(); it != (x).end(); ++it)
+#define all(x) x.begin(),x.end()
+#define D(x) cout << #x " = " << (x) << endl;
+
+template <class T> string toStr(const T &x)
+{ stringstream s; s << x; return s.str(); }
+
+template <class T> int toInt(const T &x)
+{ stringstream s; s << x; int r; s >> r; return r; }
+
+int dx[8] = {-1,-1,-1,0,1,1, 1, 0};
+int dy[8] = {-1, 0, 1,1,1,0,-1,-1};
+
+int dp[1111][1111][11];
+
+void dfs (int i, vector< vector<int> > &G, vector<int> &visited, int &size) {
+  if (!visited[i]) {
+    size ++;
+    visited[i] = true;
+    for (int j = 0; j < G[i].size(); ++j) {
+      int next = G[i][j];
+      dfs (next, G, visited, size);
+    }
+  }
+}
+
+int go (int i, int k, bool taken, int sum, vector<int> &toTake) {
+  if (dp[i][sum][taken] != -1) return dp[i][sum][taken];
+  if (i >= toTake.size()) return sum;
+
+  int a = 0, b = 0;
+  if (sum + toTake[i] <= k)
+    a = go (i + 1, k, true, sum + toTake[i], toTake);
+  b = go (i + 1, k, taken, sum, toTake);
+
+  return dp[i][sum][taken] = max(a, b);
+}
+
+/** Krustal implementation
+ *  Complexity: O(E log V)
+ **/
+
+const int mx = 1111;
+
+struct edge {
+  int start, end, weight;
+  edge(){} edge(int start, int end, int weight) : start(start), end(end), weight(weight) {}
+  bool operator < (const edge &that) const {
+    // Change < by > to find maximum spanning tree
+    return weight > that.weight;
+  }
+};
+
+/** Begin union find
+ *  Complexity: O(m log n) where m is the number of the operation
+ *              and n are the number of objects, in practice is almost O(m)
+ **/
+int p[mx];
+
+void init_set (int &n) {
+  for (int i = 0; i <= n; ++i) p[i] = i;
+}
+
+int find_set (int x) {
+  return p[x] == x ? p[x] : p[x] = find_set(p[x]);
+}
+
+void join (int x, int y) {
+  p[find_set(x)] = find_set(y);
+}
+/**  End union find **/
+
+/** e is a vector with all edges of the graph
+ *  return graph of MST
+ **/
+int krustal (vector<edge> &e, int &n, int &k, vector< vector<int> > &G, vector< vector<int> > &G2) {
+  vector<int> visited  (n + 1, 0);
+  vector<int> visited2 (n + 1, 0);
+  vector< int > toTake;
+  int rest = 0;
+
+  sort(e.begin(), e.end());
+  init_set(n);
+
+  for (int i = 0 ; i < e.size(); ++i) {
+    int u = e[i].start;
+    int v = e[i].end;
+    int w = e[i].weight;
+
+    if (find_set(u) == find_set(v)) {
+      if (!visited[u]) {
+        int sizeCycle  = 0;
+        int totalNodes = 0;
+        dfs (u, G, visited, sizeCycle);
+        dfs (u, G2, visited2, totalNodes);
+
+        if (sizeCycle <= k) {
+          toTake.push_back(sizeCycle);
+          rest += totalNodes - sizeCycle;
+        }
+      }
+    }
+
+    join(u, v);
+  }
+
+  memset(dp, -1, sizeof dp);
+  int ans = go (0, k, 0, 0, toTake);
+  int free = k - ans;
+  if (rest >= free) ans = k;
+  else ans += rest;
+  return ans;
+}
+
+int main () {
+  int n, k, b;
+  while (cin >> n >> k) {
+
+    vector<edge> v(n);
+    vector< vector<int> > G(n + 1), G2(n + 1);
+    edge e;
+
+    for (int i = 0; i < n; ++i) {
+      cin >> b;
+
+      e.start  = i + 1;
+      e.end    = b;
+      e.weight = 1;
+      v[i] = e;
+
+      G[i + 1].push_back(b);
+      G2[b].push_back(i + 1);
+    }
+
+    int ans = krustal(v, n, k, G, G2);
+    cout << ans << endl;
+  }
+}