Added older advents

advent_of_code_2018/day6/main1.cc

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+#include <iostream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+struct Point
+{
+    size_t x;
+    size_t y;
+
+    Point() 
+    : x(0), y(0)
+    { }
+
+    Point(size_t x, size_t y)
+    : x(x), y(y)
+    { }
+};
+
+istream &operator>>(istream& in, Point &point)
+{
+    cin >> point.x;
+    cin.ignore(); // ignore ','
+    cin >> point.y;
+
+    return in;
+}   
+
+inline size_t manhattan_distance(Point const &p1, Point const &p2)
+{
+    return (p1.x > p2.x ? p1.x - p2.x : p2.x - p1.x)
+        + (p1.y > p2.y ? p1.y - p2.y : p2.y - p1.y);
+}
+
+int closest(Point location, vector<Point> const &points)
+{
+    int index = -1;
+    size_t mindist = std::numeric_limits<size_t>::max();
+
+    for (size_t idx = 0; idx != points.size(); ++idx)
+    {
+        size_t distance = manhattan_distance(location, points[idx]);
+
+        if (distance == mindist)
+            index = -1;
+        else if (distance < mindist)
+        {
+            mindist = distance;
+            index = idx;
+        }
+    }
+
+    return index;
+}
+
+int main()
+{
+    size_t width = 0;
+    size_t height = 0;
+    vector<Point> points;
+
+    while(!cin.eof())
+    {
+        Point point;
+        cin >> point;
+
+        points.push_back(point);
+        width = max(width, point.x + 1);
+        height = max(height, point.y + 1);
+    }
+
+    cout << "grid size: " << width << " x " << height << "\n";
+    vector<int> counts(points.size(), 0);
+
+    for (size_t idx = 0; idx != width; ++idx)
+    {
+        for (size_t idy = 0; idy != height; ++idy)
+        {
+            int index = closest(Point{idx, idy}, points);
+            if (index == -1) continue;
+            ++counts[index];
+        }
+    }
+
+    // if a class hits the edge its infinite.
+    // we check highest and lowers rows first.
+    for (size_t idx = 0; idx != width; ++idx)
+    {
+        int index = closest(Point{idx, 0}, points);
+        int index2 = closest(Point{idx, height - 1}, points);
+        
+        if (index != -1)
+            counts[index] = -1;
+        
+        if (index2 != -1)
+            counts[index2] = -1;
+    }
+
+    //side rows
+    for (size_t idx = 0; idx != height; ++idx)
+    {
+        int index = closest(Point{0, idx}, points);
+        int index2 = closest(Point{width - 1, idx}, points);
+        
+        if (index != -1)
+            counts[index] = -1;
+        
+        if (index2 != -1)
+            counts[index2] = -1;
+    }
+
+    size_t maxclass = 0;
+    int space = counts[0];
+    for (size_t idx = 1; idx != counts.size(); ++idx)
+    {
+        if (counts[idx] > space)
+        {
+            space = counts[idx];
+            maxclass = idx;
+        }
+    }
+
+    cout << "biggest class is " << maxclass << " with a size of " << space << "\n";
+}