Added older advents

advent_of_code_2018/day3/main2.cc

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+#include <iostream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+struct Claim
+{
+    size_t id;
+    size_t px;
+    size_t py;
+    size_t width;
+    size_t height;
+};
+
+istream &operator>>(istream &in, Claim &claim)
+{
+    // reading into char in favor if in.ignore(), to automatically
+    // toss any present whitespace.
+    char at; 
+
+    cin >> at; //ignore '#'
+    in >> claim.id;
+
+    in >> at; //ignore '@'
+    in >> claim.px;
+    cin >> at; //ignore ','
+    in >> claim.py;
+
+    in >> at; //ignore ':'
+    in >> claim.width;
+    in >> at; //ignore 'x'
+    in >> claim.height;
+
+    return in;
+}
+
+void layout_claim(vector<vector<int>> &canvas, Claim const &claim)
+{
+    size_t end_x = claim.px + claim.width;
+    size_t end_y = claim.py + claim.height;
+
+    for (size_t px = claim.px; px != end_x; ++px)
+    {
+        for (size_t py = claim.py; py != end_y; ++py)
+            ++canvas[px][py];
+    }
+}
+
+bool overlaps(vector<vector<int>> &canvas, Claim const &claim)
+{
+    size_t end_x = claim.px + claim.width;
+    size_t end_y = claim.py + claim.height;
+
+    for (size_t px = claim.px; px != end_x; ++px)
+    {
+        for (size_t py = claim.py; py != end_y; ++py)
+        {
+            if (canvas[px][py] != 1)
+                return true;
+        }
+    }
+
+    return false;
+}
+
+int main()
+{
+    size_t total_width = 0;
+    size_t total_height = 0;
+    vector<Claim> claims;
+    vector<vector<int>> canvas;
+    
+    while (!cin.eof())
+    {
+        Claim claim;
+        cin >> claim;
+
+        total_width = max(total_width, claim.px + claim.width);
+        total_height = max(total_height, claim.py + claim.height);
+
+        claims.push_back(claim);
+    }
+
+    canvas.resize(total_width, vector<int>(total_height, 0));
+    for (Claim const &claim : claims)
+        layout_claim(canvas, claim);
+
+    size_t overlap = 0;
+    for (size_t py = 0; py < total_height; ++py)
+    {
+        for (size_t px = 0; px < total_width; ++px)
+        {
+            if (canvas[px][py] > 1)
+                ++overlap;
+        }
+    }
+
+    for (size_t idx = 0; idx != claims.size(); ++idx)
+    {
+        if (!overlaps(canvas, claims[idx]))
+            cout << "No overlap for " << idx << "\n";
+    }
+    
+}