Add day 9 solution

09/example

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+R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2

09/example2

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+R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20

09/rope.py

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+
+import fileinput
+
+class Rope:
+
+    def __init__(self):
+        self.head = [0,0]
+        self.tail = [0,0]
+        self.visited = set([tuple(self.tail)])
+    
+    def chatchup(self):
+        if max(abs(self.head[0] - self.tail[0]), abs(self.head[1] - self.tail[1])) <= 1: # Same pos or next to each other
+            pass
+        else:
+            if self.head[1] > self.tail[1]:
+                self.tail[1] += 1
+            elif self.head[1] < self.tail[1]:
+                self.tail[1] -= 1
+            if self.head[0] > self.tail[0]:
+                self.tail[0] += 1
+            elif self.head[0] < self.tail[0]:
+                self.tail[0] -= 1
+        self.visited.add(tuple(self.tail))
+
+    def step(self, d, count):
+        if d == "U":
+            self.head[1] += 1
+        elif d == "D":
+            self.head[1] -= 1
+        elif d == "L":
+            self.head[0] += 1
+        elif d == "R":
+            self.head[0] -= 1
+        self.chatchup()
+        if count > 1:
+            self.step(d, count-1)        
+
+class LongRope:
+
+    def __init__(self):
+        self.ropes = []
+        for _ in range(9):
+            self.ropes.append(Rope())
+
+    def step(self, d, count):
+        if d == "U":
+            self.ropes[0].head[1] += 1
+        elif d == "D":
+            self.ropes[0].head[1] -= 1
+        elif d == "L":
+            self.ropes[0].head[0] += 1
+        elif d == "R":
+            self.ropes[0].head[0] -= 1
+        self.ropes[0].chatchup()
+        for idx in range(1, len(self.ropes)):
+            self.ropes[idx].head = self.ropes[idx-1].tail
+            self.ropes[idx].chatchup()
+        if count > 1:
+            self.step(d,count-1)
+
+def solve(lines):
+    rope = Rope()
+    for d, count in map(lambda x: x.split(' '), filter(lambda x: x != "", map(lambda x: x.strip(), lines))):
+        count = int(count)
+        rope.step(d, count)
+    return len(rope.visited)
+
+def solveb(lines):
+    rope = LongRope()
+    for d, count in map(lambda x: x.split(' '), filter(lambda x: x != "", map(lambda x: x.strip(), lines))):
+        count = int(count)
+        rope.step(d, count)
+    return len(rope.ropes[-1].visited)
+
+if __name__ == "__main__":
+    print(f"Visited {solve(fileinput.input())}")
+    print(f"Visited long {solveb(fileinput.input())}")