add: GasStations

Author: Jer3myYu

java/Greedy/GasStations.java

@@ -0,0 +1,26 @@
+import java.util.Arrays;
+
+public class GasStations {
+    public int gasStations(int[] gas, int[] cost) {
+        // If the total gas is less than the total cost, completing the
+        // circuit is impossible.
+        if (Arrays.stream(gas).sum() < Arrays.stream(cost).sum()) {
+            return -1;
+        }
+        int start, tank;
+        start = tank = 0;
+        for (int i = 0; i < gas.length; i++) {
+            tank += gas[i] - cost[i];
+            // If our tank has negative gas, we cannot continue through the 
+            // circuit from the current start point, nor from any station 
+            // before or including the current station 'i'.
+            if (tank < 0) {
+                // Set the next station as the new start point and reset the 
+                // tank.
+                start = i + 1;
+                tank = 0;
+            }
+        }
+        return start;
+    }
+}