Add problem 134 - Gas Station

Author: anirudhology

problems/greedy/gas_station.py

@@ -0,0 +1,21 @@
+from typing import List
+
+
+class GasStation:
+    @staticmethod
+    def canCompleteCircuit(gas: List[int], cost: List[int]) -> int:
+        # Local effective fuel - fuel if we start from current index
+        local_fuel = 0
+        # Global effective fuel - fuel left after the journey
+        global_fuel = 0
+        # Index to start the journey from
+        index = 0
+        # Process the arrays
+        for i in range(len(gas)):
+            local_fuel += gas[i] - cost[i]
+            global_fuel += gas[i] - cost[i]
+            # Check if the fuel becomes negative
+            if local_fuel < 0:
+                local_fuel = 0
+                index = i + 1
+        return index if global_fuel >= 0 else -1

tests/greedy/gas_station_test.py

@@ -0,0 +1,40 @@
+import unittest
+
+from problems.greedy.gas_station import GasStation
+
+
+class TestGasStation(unittest.TestCase):
+
+    def test_can_complete_circuit_basic(self):
+        gas_station = GasStation()
+        gas = [1, 2, 3, 4, 5]
+        cost = [3, 4, 5, 1, 2]
+        self.assertEqual(gas_station.canCompleteCircuit(gas, cost), 3)
+
+    def test_can_complete_circuit_no_solution(self):
+        gas_station = GasStation()
+        gas = [2, 3, 4]
+        cost = [3, 4, 5]
+        self.assertEqual(gas_station.canCompleteCircuit(gas, cost), -1)
+
+    def test_can_complete_circuit_single_station(self):
+        gas_station = GasStation()
+        gas = [5]
+        cost = [4]
+        self.assertEqual(gas_station.canCompleteCircuit(gas, cost), 0)
+
+    def test_can_complete_circuit_all_stations_equal(self):
+        gas_station = GasStation()
+        gas = [1, 1, 1, 1]
+        cost = [1, 1, 1, 1]
+        self.assertEqual(gas_station.canCompleteCircuit(gas, cost), 0)
+
+    def test_can_complete_circuit_multiple_solutions(self):
+        gas_station = GasStation()
+        gas = [2, 3, 4]
+        cost = [2, 1, 2]
+        self.assertEqual(gas_station.canCompleteCircuit(gas, cost), 0)  # Returns the first valid start
+
+
+if __name__ == '__main__':
+    unittest.main()