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GasStation.java
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38 lines (34 loc) · 1.05 KB
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package algorithm.lc;
/**
* 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 {
// O(1) space, O(n) time
public class Solution {
public int canCompleteCircuit(int[] gas, int[] cost) {
// Note: The Solution object is instantiated only once and is reused by
// each test case.
int start = 0, total = 0, remain = 0;
for (int i = 0; i < gas.length; ++i) {
remain += gas[i] - cost[i];
total += gas[i] - cost[i];
if (remain < 0) {
start = i + 1; // i cannot reach to i + 1
remain = 0;
}
}
return total < 0? -1 : start;
}
}
}