Algorithms—134.Gas Station

思路：每个加油站提供的油减去下一段路上耗费的油，生成新的数组。循环数组长度2倍的量，找出其中一段长度为数组长且每部的剩余油量都不小于0的；

public class Solution {
public int canCompleteCircuit(int[] gas, int[] cost) {
int[] n = new int[gas.length];
for (int i = 0; i < n.length; i++) {
n[i] = gas[i] - cost[i];
}
int sum = 0;
int begin = 0;
int truebegin=0;
for (int i = 0; i < n.length*2; i++) {
sum += n[i%n.length];
while (sum < 0) {
sum -= n[truebegin];
begin++;
truebegin=begin%n.length;
}
if (i-begin>=n.length) {
return truebegin;
}
}
return -1;
}
}