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134.java
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134.java
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sample 0 ms submission
class Solution {
/**
*O(N);该方法比较妙。
*/
public int canCompleteCircuit(int[] gas, int[] cost) {
if (gas == null || cost == null || gas.length == 0 || cost.length == 0) return -1;
int startGasStation = 0, currGas = 0, remindGas = 0;//currGas当前油量;remindGas总共油剩余量
for (int i = 0; i < gas.length; i++) {//从第一个油站开始加油
remindGas += gas[i] - cost[i];
currGas += gas[i] - cost[i];
if (currGas < 0) {//当前流量小于0
currGas = 0;
startGasStation = i + 1;
}
}
return remindGas >= 0 ? startGasStation : -1;
}
}
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sample 34436 kb submission
class Solution {
public int canCompleteCircuit(int[] gas, int[] cost) {
int[] left_gas = new int[gas.length];
int sum_gas = 0;
for (int i = 0; i < gas.length; i++) {
left_gas[i] = gas[i] - cost[i];
sum_gas += left_gas[i];
}
if (sum_gas < 0) return -1;
int index = -1;
int pos_sum_gas = 0;
int maximum_gas = -1;
int len = 0;
for (int i = 0; i < gas.length; i++) {
pos_sum_gas += left_gas[i];
if (pos_sum_gas < 0) {
pos_sum_gas = 0;
len = 0;
maximum_gas = 0;
} else {
if (pos_sum_gas > maximum_gas) {
index = i - len;
maximum_gas = pos_sum_gas;
}
len++;
}
}
return index;
}
}
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