public class Solution {

public int canCompleteCircuit(int[] gas, int[] cost) {

if (gas == null || cost == null || gas.length != cost.length)

return -1;

int[] gasLeft = new int[gas.length];

for (int i = 0; i < gas.length;) {

int j = 0;

if (gas[i] >= cost[i]) {

int remainGas = 0;

for (; j < gas.length && remainGas >= 0; j++) {

int idx = (i + j) % gas.length;

remainGas += gas[idx] - cost[idx];

}

if (j == gas.length && remainGas >= 0)

return i;

}

if (j > 0)

i += j;

else

i++;

}

return -1;

}

}