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.
The solution is guaranteed to be unique.
Solution:
1. If from start we cannot get to station i, we know from start, no one can get to station i. Therefore station 0 to i can be safely removed from candidates.
2. If from to end, the total gas - total cost < 0, we know it is impossible from any station to drive a loop. So there is no solution.
Code:
public class Solution { public int canCompleteCircuit(int[] gas, int[] cost) { int totalGas = 0; int leftOver = 0; int res = 0; for (int i = 0; i < gas.length; i++) { totalGas += gas[i] - cost[i]; leftOver += gas[i] - cost[i]; if (leftOver < 0) { leftOver = 0; res = i + 1; } } return totalGas >= 0 ? res : -1; } }