Added 2020 (python)

2020/13/input

@@ -0,0 +1,2 @@
+1002462
+37,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,x,x,x,601,x,x,x,x,x,x,x,x,x,x,x,19,x,x,x,x,17,x,x,x,x,x,23,x,x,x,x,x,29,x,443,x,x,x,x,x,x,x,x,x,x,x,x,13

2020/13/prog.py

@@ -0,0 +1,52 @@
+from math import gcd
+
+def get_input(sample = False):
+    with open("sample" if sample else 'input', 'r') as f:
+        ret = []
+        lines = f.readlines()
+        ret.append(int(lines[0]))
+        ret.append([int(x) if x != "x" else x for x in lines[1].split(',')])
+
+        return ret
+
+def get_next_bus_departure(bus_id: int, cur_time: int):
+    return bus_id * math.ceil(cur_time / bus_id)
+
+def get_result(data: list, part = 1):
+    cur_time = data[0]
+    busses = data[1]
+
+    if part == 1:
+        eta_n_bus = {}
+        for bus in busses:
+            if bus == 'x': continue
+            
+            eta = get_next_bus_departure(bus, cur_time)
+            eta_n_bus[eta] = bus
+
+        earliest = min(eta_n_bus.keys())
+        earliest_bus = eta_n_bus[earliest]
+        waiting_time = earliest - cur_time
+        return waiting_time * earliest_bus
+    else:
+        step = busses[0]
+        bus_n_offsets = [(bus, offset) for offset, bus in enumerate(busses) if bus != 'x']
+        time = 0
+
+        for bus, offset in bus_n_offsets[1:]:
+            while True:
+                time += step
+                if (time + offset) % bus == 0:
+                    step = lcm(step, bus)
+                    break
+        return time
+                    
+        
+
+
+def lcm(a, b):
+    return abs(a*b) // gcd(a, b)
+
+
+if __name__ == "__main__":
+    print(get_result(get_input(), part = 2))

2020/13/sample

@@ -0,0 +1,2 @@
+939
+7,13,x,x,59,x,31,19

2020/13/test.py

@@ -0,0 +1,20 @@
+from prog import *
+import unittest
+
+class Methods(unittest.TestCase):
+    def test_get_input(self):
+        inp = get_input(sample = True)
+        self.assertEqual(inp, [939, [7, 13, 'x', 'x', 59, 'x', 31, 19]])
+
+class Result(unittest.TestCase):
+    def setUp(self):
+        self.inp = get_input(sample = True)
+
+    def test_part_1(self):
+        self.assertEqual(get_result(self.inp), 295)
+
+    def test_part_2(self):
+        self.assertEqual(get_result([0, [7, 13]], part = 2), 77)
+        self.assertEqual(get_result([0, [17, 'x', 13, 19]], part = 2), 3417)
+        self.assertEqual(get_result(self.inp, part = 2), 1068781)
+