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.
一刷
题解：
如果A不能到达B，那么AB间的所有station都不能到达B
如果总的cost>gas, 那么从所有的stop都不能完成一次循环
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++){
tank += gas[i] - cost[i];
if(tank<0){
start = i+1;
total += tank;
tank = 0;
}
}
return total+tank<0? -1:start;
}
}
二刷
思路同1刷
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++){
tank+= gas[i] - cost[i];
if(tank<0){
start = i+1;
total+= tank;
tank = 0;
}
}
if(total+tank>=0) return start;
else return -1;
}
}
