gas station

leetcode/GasStation.cpp

@@ -0,0 +1,35 @@
+#include <iostream>
+#include <vector>
+using namespace std;
+
+int canCompleteCircuit(vector<int> &gas, vector<int> &cost)
+{
+    // first of all we need to check whether we've sfficient fuel or not.
+    int total_cost = 0, total_fuel = 0, n = cost.size();
+    for (int i = 0; i < n; i++)
+    {
+        total_cost += cost[i];
+        total_fuel += gas[i];
+    }
+    // If the total fuel is lesser than the cost then definitely we can't cover the whole cicular tour.
+    if (total_fuel < total_cost)
+    {
+        return -1;
+    }
+
+    // If the total fuel is sufficient enough to cover the circular tour then definitely an answer exists
+    int curr_fuel = 0, start = 0; // start with zero fuel.
+    for (int i = 0; i < n; i++)
+    {
+        // If at any point our balance/ current fuel is negative that means we can't come to the i'th petrol pump from the previous pump beacuse our fuel won't allow us to cover such distance.
+        // So we'll make the i'th pump as the start point ans proceed. Simultaneously we'll make the current fuel to be 0 as we're starting freshly.
+        if (curr_fuel < 0)
+        {
+            start = i;
+            curr_fuel = 0;
+        }
+        // at any station we'll fill petrol and pay the cost to go to the next station . so current fuel would be the following.
+        curr_fuel += (gas[i] - cost[i]);
+    }
+    return start;
+}