Gas Station

Author: nikoo28

src/main/java/leetcode/medium/GasStation.java

@@ -0,0 +1,35 @@
+package leetcode.medium;
+
+public class GasStation {
+
+  int canCompleteCircuit(int[] gas, int[] cost) {
+    int totalGas = 0, totalCost = 0;
+
+    // Calculate total gas and total cost
+    for (int i = 0; i < gas.length; i++) {
+      totalGas += gas[i];
+      totalCost += cost[i];
+    }
+
+    // If total gas is less than total cost, return -1
+    if (totalGas < totalCost) {
+      return -1;
+    }
+
+    int currentGas = 0, startIndex = 0;
+    // Iterate through the gas stations
+    for (int i = 0; i < gas.length; i++) {
+      currentGas += gas[i] - cost[i];
+
+      // If current gas is negative, reset start index and current gas
+      if (currentGas < 0) {
+        startIndex = i + 1;
+        currentGas = 0;
+      }
+    }
+
+    // Return the starting index if a valid circuit exists
+    return startIndex;
+  }
+
+}

src/test/java/leetcode/medium/GasStationTest.java

@@ -0,0 +1,42 @@
+package leetcode.medium;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class GasStationTest {
+
+  private final GasStation gasStation;
+
+  GasStationTest() {
+    gasStation = new GasStation();
+  }
+
+  @Test
+  void testCanCompleteCircuit1() {
+    int[] gas = {1, 2, 3, 4, 5};
+    int[] cost = {3, 4, 5, 1, 2};
+    assertEquals(3, gasStation.canCompleteCircuit(gas, cost));
+  }
+
+  @Test
+  void testCanCompleteCircuit2() {
+    int[] gas = {2, 3, 4};
+    int[] cost = {3, 4, 3};
+    assertEquals(-1, gasStation.canCompleteCircuit(gas, cost));
+  }
+
+  @Test
+  void testCanCompleteCircuit3() {
+    int[] gas = {5, 1, 2, 3, 4};
+    int[] cost = {4, 4, 1, 5, 1};
+    assertEquals(4, gasStation.canCompleteCircuit(gas, cost));
+  }
+
+  @Test
+  void testCanCompleteCircuit4() {
+    int[] gas = {1, 2, 3};
+    int[] cost = {2, 2, 2};
+    assertEquals(1, gasStation.canCompleteCircuit(gas, cost));
+  }
+}