*Hey, it’s your favorite cult leader here 🐱👤*

*On Thursdays, I will send you a problem + its solution. These solutions will help you reinforce your fundamental concepts, improve your problem-solving, and kill those Leetcode-Style Interviews. 🔥🔥💹💹*

*To get access to all my articles and support my crippling chocolate milk addiction, consider subscribing if you haven’t already!*

*p.s. you can learn more about the paid plan here.*

This can be a tricky problem if you don’t know what to look for.

In honor of those of you that struggled with this problem here is a meme to lessen your pain. To make the newsletter more fun to read, I am looking to throw in more memes/art/anything else. If any of you have anything to share, you can always reach me through my Instagram or other social media linked at the end of all my articles.

Back to the problem at hand.

This problem can be found as problem **134. Gas Station**

**Problem**

There are `n`

gas stations along a circular route, where the amount of gas at the `ith`

station is `gas[i]`

.

You have a car with an unlimited gas tank and it costs `cost[i]`

of gas to travel from the `ith`

station to its next `(i + 1)th`

station. You begin the journey with an empty tank at one of the gas stations.

Given two integer arrays `gas`

and `cost`

, return *the starting gas station's index if you can travel around the circuit once in the clockwise direction, otherwise return* `-1`

. If there exists a solution, it is **guaranteed** to be **unique**

**Example 1:**

```
Input: gas = [1,2,3,4,5], cost = [3,4,5,1,2]
Output: 3
Explanation:
Start at station 3 (index 3) and fill up with 4 unit of gas. Your tank = 0 + 4 = 4
Travel to station 4. Your tank = 4 - 1 + 5 = 8
Travel to station 0. Your tank = 8 - 2 + 1 = 7
Travel to station 1. Your tank = 7 - 3 + 2 = 6
Travel to station 2. Your tank = 6 - 4 + 3 = 5
Travel to station 3. The cost is 5. Your gas is just enough to travel back to station 3.
Therefore, return 3 as the starting index.
```

**Example 2:**

```
Input: gas = [2,3,4], cost = [3,4,3]
Output: -1
Explanation:
You can't start at station 0 or 1, as there is not enough gas to travel to the next station.
Let's start at station 2 and fill up with 4 unit of gas. Your tank = 0 + 4 = 4
Travel to station 0. Your tank = 4 - 3 + 2 = 3
Travel to station 1. Your tank = 3 - 3 + 3 = 3
You cannot travel back to station 2, as it requires 4 unit of gas but you only have 3.
Therefore, you can't travel around the circuit once no matter where you start.
```

**Constraints:**

`n == gas.length == cost.length`

`1 <= n <= 105`

`0 <= gas[i], cost[i] <= 104`

## Keep reading with a 7-day free trial

Subscribe to Technology Made Simple to keep reading this post and get 7 days of free access to the full post archives.