Gas Station: coding question

Problem

A circular road has n gas stations, with the numbers 0 to n - 1. Station i gives you gas[i] units of fuel. The drive from station i to the next station uses cost[i] units of fuel.

The next station after station n - 1 is station 0. Your car starts with an empty tank, and the tank has no size limit.

Choose a start station and drive one full circle in the forward direction. Return the index of the start station that lets you complete the circle. If no start station works, return -1.

If a solution exists, only one start station works.

Example 1

Input:: gas = [1,6,2,3], cost = [3,2,5,2]
Output:: 1
Explanation:: Start at station 1 with 6 units. You arrive at station 2 with 4 units, at station 3 with 1 unit, and at station 0 with 2 units. Then you return to station 1 with 0 units.

Example 2

Input:: gas = [3,1,2], cost = [2,3,3]
Output:: -1
Explanation:: The stations give 6 units of fuel in total, but the full circle uses 8 units. No start station works.

Constraints

n == gas.length == cost.length
1 <= n <= 10^5
0 <= gas[i], cost[i] <= 10^4

SysRound wrote this statement. A reference solution checks every example.

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Sources · 2 references

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Hello Interview · 2 records

Bloomberg
Leetcode 134. Gas Station
Reported Mar 23, 2026 · 2 source reports
JUNIOR, SENIOR
Source snapshot: Nov 12, 2026
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Expedia
Leetcode 134. Gas Station
Reported Jun 4, 2026 · 1 source report
MID_LEVEL
Source snapshot: Nov 12, 2026
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LeetCode company tags · 4 records

Adobe
Gas Station
Reported date not specified · Source window: 6mo
Source snapshot: Oct 20, 2026
Source frequency score: 79.4. This is not an interview probability.
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Goldman Sachs
Gas Station
Reported date not specified · Source window: 6mo

Problem

A circular road has n gas stations, with the numbers 0 to n - 1. Station i gives you gas[i] units of fuel. The drive from station i to the next station uses cost[i] units of fuel.

The next station after station n - 1 is station 0. Your car starts with an empty tank, and the tank has no size limit.

Choose a start station and drive one full circle in the forward direction. Return the index of the start station that lets you complete the circle. If no start station works, return -1.

If a solution exists, only one start station works.

Example 1

Input:: gas = [1,6,2,3], cost = [3,2,5,2]
Output:: 1
Explanation:: Start at station 1 with 6 units. You arrive at station 2 with 4 units, at station 3 with 1 unit, and at station 0 with 2 units. Then you return to station 1 with 0 units.

Example 2

Input:: gas = [3,1,2], cost = [2,3,3]
Output:: -1
Explanation:: The stations give 6 units of fuel in total, but the full circle uses 8 units. No start station works.

Constraints

n == gas.length == cost.length
1 <= n <= 10^5
0 <= gas[i], cost[i] <= 10^4

SysRound wrote this statement. A reference solution checks every example.

Gas Station

Problem

Example 1

Example 2

Constraints

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Gas Station

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Example 1

Example 2

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