Day 9

Day9/part1.cpp

@@ -0,0 +1,94 @@
+#include <iostream>
+#include <string>
+#include <set>
+#include <utility>
+
+using namespace std;
+
+struct Rope
+{
+    Rope(pair<int, int> head, pair<int, int> tail) : head{head}, tail{tail} {}
+    pair<int, int> head, tail;
+
+};
+
+Rope move_rope(Rope rope, int dx, int dy);
+
+int main(int argc, char* argv[])
+{
+    Rope rope({0,0}, {0,0});
+    set<pair<int, int>> visited;
+
+    string line;
+    while(getline(cin, line))
+    {
+        char dir = line[0];
+        int amount = stoi(line.substr(2));
+        int dx = (dir=='R')?1:((dir=='L')?-1:0);
+        int dy = (dir=='U')?1:((dir=='D')?-1:0);
+
+        for(int i = 0; i < amount; i++)
+        {
+            rope = move_rope(rope, dx, dy);
+            visited.insert(rope.tail);
+        }
+    }
+
+    cout << visited.size() << endl;
+}
+
+Rope move_rope(Rope rope, int dx, int dy)
+{
+    rope.head.first += dx;
+    rope.head.second += dy;
+
+    if (rope.head.first == rope.tail.first)
+    { //same x
+        if (rope.head.second > rope.tail.second)
+        {
+            rope.tail.second = rope.head.second-1;
+        }
+        else if (rope.head.second < rope.tail.second)
+        {
+            rope.tail.second = rope.head.second+1;
+        }
+    }
+    else if (rope.head.second == rope.tail.second)
+    { //same y
+        if (rope.head.first > rope.tail.first)
+        {
+            rope.tail.first = rope.head.first-1;
+        }
+        else if (rope.head.first < rope.tail.first)
+        {
+            rope.tail.first = rope.head.first+1;
+        }
+    }
+    else
+    { //diagonal
+        if (abs(rope.head.first-rope.tail.first) == 1 && abs(rope.head.second-rope.tail.second) == 1)
+        {
+            return rope;
+        }
+
+        if (rope.head.first-rope.tail.first > 0)
+        {
+            rope.tail.first++;
+        }
+        else
+        {
+            rope.tail.first--;
+        }
+
+        if (rope.head.second-rope.tail.second > 0)
+        {
+            rope.tail.second++;
+        }
+        else
+        {
+            rope.tail.second--;
+        }
+    }
+
+    return rope;
+}