feat(day 57): calculate communication time across satellite route with preccise delay logic

Author: JohnSunny21

FreeCodeCamp/CodingQ/SpaceWeek/SpaceWeek3.py

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+"""
+Space Week Day 3: Phone Home
+For day three of Space Week, you are given an array of numbers representing distances (in kilometers) between yourself, satellites, and your home planet in a communication route. Determine how long it will take a message sent through the route to reach its destination planet using the following constraints:
+
+The first value in the array is the distance from your location to the first satellite.
+Each subsequent value, except for the last, is the distance to the next satellite.
+The last value in the array is the distance from the previous satellite to your home planet.
+The message travels at 300,000 km/s.
+Each satellite the message passes through adds a 0.5 second transmission delay.
+Return a number rounded to 4 decimal places, with trailing zeros removed.
+"""
+
+import unittest
+
+class SpaceWeekTest(unittest.TestCase):
+
+    def test1(self):
+        self.assertEqual(send_message([300000,300000]),2.5)
+
+    def test2(self):
+        self.assertEqual(send_message([384400,384400]),3.0627)
+
+    def test3(self):
+        self.assertEqual(send_message([54600000,54600000]),364.5)
+    
+    def test4(self):
+        self.assertEqual(send_message([1000000,500000000,1000000]),1674.3333)
+
+    def test5(self):
+        self.assertEqual(send_message([10000, 21339, 50000, 31243, 10000]),2.4086)
+
+    def test6(self):
+        self.assertEqual(send_message([802101, 725994, 112808, 3625770, 481239]),21.1597)
+
+
+
+
+
+
+
+
+
+
+def send_message(route):
+
+
+    total_distance = sum(route)
+    total_num_of_satellites = route[:-1]
+
+    total_time = (total_distance / 300000) + len(total_num_of_satellites) * 0.5
+
+    return round(total_time,4)
+
+"""
+
+ Why round(total_time, 4) gives 4 decimal places
+Yes, round(total_time, 4) returns a float rounded to 4 decimal places. But floats in Python don’t preserve trailing zeros — so round(2.5, 4) gives 2.5, not 2.5000.
+To force 4 decimal places, we use:
+format(round(total_time, 4), '.4f')  # → '2.5000'
+
+
+Then we strip trailing zeros with:
+.rstrip('0')  # → '2.5'
+
+
+
+❓ Why .rstrip('.') is used
+This is a defensive edge-case guard. After stripping trailing zeros, you might end up with a string like:
+'2.'  # ← not ideal
+
+
+This happens when the number is something like 2.0000:
+- format(..., '.4f') → '2.0000'
+- .rstrip('0') → '2.'
+- .rstrip('.') → '2'
+So .rstrip('.') ensures you don’t return a number with a dangling decimal point.
+
+🧪 Example
+total_time = 2.0000
+formatted = format(round(total_time, 4), '.4f')  # '2.0000'
+cleaned = formatted.rstrip('0').rstrip('.')      # '2'
+
+
+
+🔍 Did the question require it?
+No, the prompt didn’t explicitly mention this edge case. But it did say:
+“Return a number rounded to 4 decimal places, with trailing zeros removed.”
+
+So .rstrip('.') is a safe polish to prevent awkward outputs like '2.'.
+
+
+
+"""
+def send_message_edge(route):
+    speed = 300_000  # km/s
+
+    travel_time = sum(route) / speed
+    satellite_delay = 0.5 * (len(route) - 1)
+    total_time = travel_time + satellite_delay
+
+    # The result is returning the string but we need the number with the decimal places
+    refined_time = format(round(total_time,4), '.4f').rstrip('0').rstrip('.') if '.' in str(total_time) else str(total_time)
+
+    return float(refined_time)
+
+if __name__ == "__main__":
+
+    print(send_message([300000,300000]))
+    unittest.main()