[LeetCode 134]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.
*
*/
public class GasStation {
// 16 / 16 test cases passed.
// Status: Accepted
// Runtime: 247 ms
// Submitted: 0 minutes ago
//時間復雜度O(n) 空間復雜度O(1)
public int canCompleteCircuit(int[] gas, int[] cost) {
int remaining = 0; //從開始點到當前點剩余的油量
int begin = -1; //開始點下標
int total = 0; // 判斷是否有解
for (int i = 0; i < cost.length; i++) {
remaining += gas[i] - cost[i];
total += gas[i] - cost[i];
if(remaining < 0) {
remaining = 0;
begin = i;
}
}
return (total < 0) ? -1 : begin + 1;
}
public static void main(String[] args) {
}
}
