BiruLyu
8/3/2017 - 8:46 PM

## 134. Gas Station(#).java

``````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;
}
};``````
``````public class Solution {
public int canCompleteCircuit(int[] gas, int[] cost) {
int start = 0, total = 0, tank = 0;
for (int i = 0; i < gas.length; i++) {
if ((tank = tank + gas[i] - cost[i]) < 0) {
start = i + 1;
total += tank;
tank = 0;
}
}
return total + tank < 0 ? -1 : start;
}
}
/*
[4]
[5]
[1,2,3,4,5]
[2,5,1,2,1]
[1,2]
[2,1]
*/``````
``````public class Solution {
public int canCompleteCircuit(int[] gas, int[] cost) {
if  (gas == null || cost == null || gas.length < 1 || cost.length < 1) return -1;
int len = gas.length;
int[] left = new int[len];
int sum = 0;
for (int i = 0; i < len; i++) {
left[i] = gas[i] - cost[i];
sum += left[i];
}
if (sum < 0) return -1;
int curLeft = 0;
int res = 0;
for (int i = 0; i < len; i++) {
curLeft += left[i];
if (curLeft < 0) {
res = i + 1;
curLeft = 0;
}
}
return res;
}
}``````