AntsMeet.cpp

Author: aseembrahma

AntsMeet.cpp

@@ -0,0 +1,213 @@
+#include <iostream>
+#include <iterator>
+#include <algorithm>
+#include <map>
+#include <vector>
+#include <iomanip>
+#include <sstream> 
+#include <queue>
+#include <string>
+#include <cmath>
+#include <set>
+#include <limits>
+#include <numeric>
+#include <bitset>
+#include <stack>
+#include <utility>
+#include <unordered_set>
+#include <unordered_map>
+
+#define DEBUG 0
+#define ARR_SIZE(x) ((sizeof(x)) / (sizeof(x[0])))
+#define INF_INT numeric_limits<int>::max()
+#define MIN_INT numeric_limits<int>::min()
+
+using namespace std;
+
+typedef unsigned long long ULL;
+typedef long long LL;
+typedef pair<int, int> pii;
+
+vector<string> &split(const string &s, char delim, vector<string> &elems) {
+    stringstream ss(s);
+    string item;
+    while (getline(ss, item, delim)) {
+        elems.push_back(item);
+    }
+    return elems;
+}
+
+vector<string> split(const string &s, char delim) {
+    vector<string> elems;
+    split(s, delim, elems);
+    return elems;
+}
+
+template <typename K, typename V>
+V GetWithDef(const  std::map <K,V> & m, const K & key, const V & defval ) {
+    typename std::map<K,V>::const_iterator it = m.find( key );
+    if ( it == m.end() ) {
+        return defval;
+    }
+    else {
+        return it->second;
+    }
+}
+
+template<typename T>
+void print_vector(const vector<T> &v) {
+  cerr << " { ";
+  for (typename vector<T>::const_iterator it = v.begin(); it != v.end(); ++it) {
+    cerr << *it << ", ";
+  }
+  cerr << " } " << endl;
+}
+
+class AntsMeet {
+  /*
+   */
+
+public:
+  int countAnts(vector<int> x, vector<int> y, string direction) {
+    int n = x.size();
+    vector<vector<int> > points(n, vector<int>(2, 0));
+    vector<int> dir(n, 0);
+    typedef pair<int, pii> piii;
+    priority_queue<piii, vector<piii>, greater<piii> > pq;
+    unordered_map<char, int> m;
+
+    m['N'] = 1;
+    m['S'] = -1;
+    m['E'] = 2;
+    m['W'] = -2;
+
+    for (int i = 0; i < n; ++i) {
+      points[i][0] = x[i];
+      points[i][1] = y[i];
+      dir[i] = m[direction[i]];
+    }
+
+    for (int i = 0; i < n; ++i) {
+      for (int j = i + 1; j < n; ++j) {
+        // points travelling in the same direction cannot meet
+        if (dir[i] == dir[j]) {
+          continue;
+        }
+
+        if (abs(dir[i]) == abs(dir[j])) {
+          int abs_dir = abs(dir[i]);
+          if (points[i][abs_dir - 1] != points[j][abs_dir - 1]) {
+            continue;
+          }
+
+          if ((points[i][abs_dir % 2] * dir[i]) +
+              (points[j][abs_dir % 2] * dir[j]) < 0) {
+            pq.push(
+              make_pair(
+                abs(points[i][abs_dir % 2] - points[j][abs_dir % 2]),
+                make_pair(i, j)));
+          }
+        }
+        else {
+          // travelling horizontally, vertically
+          int h = i, v = j;
+
+          if (1 == abs(dir[i]))
+            swap(h, v);
+
+          int h_dist = points[v][0] - points[h][0];
+          int v_dist = points[h][1] - points[v][1];
+
+          // the horizontal
+          if (abs(h_dist) == abs(v_dist) &&
+              (h_dist * dir[h]) > 0 &&
+              (v_dist * dir[v]) > 0) {
+            pq.push(make_pair(abs(h_dist) * 2, make_pair(h, v)));
+          }
+        }
+      }
+    }
+
+    unordered_set<int> s;
+    for (int i = 0; i < n; ++i)
+      s.insert(i);
+
+    while (!pq.empty()) {
+      pair<int, pii> t = pq.top();
+      pq.pop();
+
+      if (s.find(t.second.first) != s.end() &&
+          s.find(t.second.second) != s.end()) {
+
+        unordered_set<int> s_temp;
+
+        /*
+        cout << "removing" << endl;
+        print_vector(points[t.second.first]);
+        print_vector(points[t.second.second]);
+        */
+
+        s_temp.insert(t.second.first);
+        s_temp.insert(t.second.second);
+        while (!pq.empty()) {
+          pair<int, pii> p = pq.top();
+          if (p.first != t.first) {
+            break;
+          }
+          else {
+            pq.pop();
+            if (s.find(p.second.first) != s.end() &&
+                s.find(p.second.second) != s.end()) {
+              /*
+              cout << "removing2" << endl;
+              print_vector(points[p.second.first]);
+              print_vector(points[p.second.second]);
+              */
+
+              s_temp.insert(p.second.first);
+              s_temp.insert(p.second.second);
+            }
+          }
+        }
+
+        for (unordered_set<int>::iterator it = s_temp.begin();
+             it != s_temp.end();
+             ++it)
+          s.erase(*it);
+      }
+    }
+    return s.size();
+  }
+
+  bool runTest(vector<int> x, vector<int> y, string direction, int solution) {
+    int output = countAnts(x, y, direction);
+
+    if (output != solution)
+    {
+      cerr << "Failed for " << endl;
+      print_vector(x);
+      print_vector(y);
+      cout << direction << endl;
+      cerr << "Expected: " << solution << endl;
+      cerr << "Found instead: " << output << endl;
+      return false;
+    }
+    else {
+      return true;
+    }
+  }
+};
+
+int main(int argc, char* argv[]) {
+  AntsMeet test;
+  {
+    test.runTest({0,10,20,30}, {0,10,20,30}, "NWNE", 2);
+    test.runTest({-10,0,0,10}, {0,-10,10,0}, "NEWS", 0);
+    test.runTest({-1,-1,-1,0,0,0,1,1,1}, {-1,0,1,-1,0,1,-1,0,1}, "ESEWNNEWW", 4);
+    test.runTest({4,7,6,2,6,5,7,7,8,4,7,8,8,8,5,4,8,9,1,5,9,3,4,0,0,1,0,7,2,6,9,6,3,0,5,5,1,2,0,4,9,7,7,1,8,1,9,2,7,3}, {2,3,0,6,8,4,9,0,5,0,2,4,3,8,1,5,0,7,3,7,0,9,8,1,9,4,7,8,1,1,6,6,6,2,8,5,1,9,0,1,1,1,7,0,2,5,4,7,5,3}, "SSNWSWSENSWSESWEWSWSENWNNNESWSWSWWSSWEEWWNWWWNWENN", 25);
+    test.runTest({478,-664,759,434,-405,513,565,-396,311,-174,56,993,251,-341,993,-112,242,129,383,513,-78,-341,-148,129,423
+    ,493,434,-405,478,-148,929,251,56,242,929,-78,423,-664,802,251,759,383,-112,-591,-591,-248,660,660,735,493}, {-186,98,948,795,289,-678,948,-170,-195,290,-354,-424,289,-157,-166,150,706,-678,684,-294,-234,36,36,-294,-216
+    ,-234,427,945,265,-157,265,715,275,715,-186,337,798,-170,427,706,754,961,286,-216,798,286,961,684,-424,337}, "WNSNNSSWWWEENWESNSWSWSEWWEWEWWWNWESNSSNNSNNWWWNESE", 44);
+  }
+}
+