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Total Accepted: 83932
Total Submissions: 289062
Difficulty: Medium
Contributor: LeetCode
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.
// O(1) space O(n) running time solution
class Solution {
public:
int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {
int start = gas.size()-1;
int end = 0;
int sum = gas[start] - cost[start];
while (start > end) {
if (sum >= 0) {
sum += gas[end] - cost[end];
++end;
}
else {
--start;
sum += gas[start] - cost[start];
}
}
return sum >= 0 ? start : -1;
}
};
