GasStation.java

/**
 * There are N gas stations along a circular route, where the amount of gas at station i is gas[i].
 *
 * <p>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.
 *
 * <p>Return the starting gas station's index if you can travel around the circuit once, otherwise
 * return -1.
 *
 * <p>Note:
 *
 * <p>The solution is guaranteed to be unique.
 */
public class GasStation {
  public int canCompleteCircuit(int[] gas, int[] cost) {
    int sum = 0, total = 0, len = gas.length, index = -1;
    for (int i = 0; i < len; i++) {
      sum += gas[i] - cost[i];
      total += gas[i] - cost[i];
      if (sum < 0) {
        index = i;
        sum = 0;
      }
    }
    return total >= 0 ? index + 1 : -1;
  }
}