Gas Station

There are N gas stations along a circular route, where the amount of gas at station i is gas[i].

You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its next station (i+1). You begin the journey with an empty tank at one of the gas stations.

Return the starting gas station’s index if you can travel around the circuit once, otherwise return -1.

Note:

The solution is guaranteed to be unique.

Solution:

  1. public class Solution {
  2.   public int canCompleteCircuit(int[] gas, int[] cost) {
  3.     int pos = -1;
  4.     int curr = 0, total = 0;
  6.     for (int i = 0; i < gas.length; i++) {
  7.       int diff = gas[i] - cost[i];
  9.       curr += diff;
  10.       total += diff;
  12.       if (curr < 0) {
  13.         curr = 0;
  14.         pos = i;
  15.       }
  16.     }
  18.     if (total >= 0) {
  19.       return pos + 1;
  20.     }
  22.     return -1;
  23.   }
  24. }