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45 lines
2.2 KiB
HTML
45 lines
2.2 KiB
HTML
<p>There are <code>n</code> gas stations along a circular route, where the amount of gas at the <code>i<sup>th</sup></code> station is <code>gas[i]</code>.</p>
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<p>You have a car with an unlimited gas tank and it costs <code>cost[i]</code> of gas to travel from the <code>i<sup>th</sup></code> station to its next <code>(i + 1)<sup>th</sup></code> station. You begin the journey with an empty tank at one of the gas stations.</p>
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<p>Given two integer arrays <code>gas</code> and <code>cost</code>, return <em>the starting gas station's index if you can travel around the circuit once in the clockwise direction, otherwise return</em> <code>-1</code>. If there exists a solution, it is <strong>guaranteed</strong> to be <strong>unique</strong>.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> gas = [1,2,3,4,5], cost = [3,4,5,1,2]
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<strong>Output:</strong> 3
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<strong>Explanation:</strong>
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Start at station 3 (index 3) and fill up with 4 unit of gas. Your tank = 0 + 4 = 4
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Travel to station 4. Your tank = 4 - 1 + 5 = 8
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Travel to station 0. Your tank = 8 - 2 + 1 = 7
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Travel to station 1. Your tank = 7 - 3 + 2 = 6
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Travel to station 2. Your tank = 6 - 4 + 3 = 5
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Travel to station 3. The cost is 5. Your gas is just enough to travel back to station 3.
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Therefore, return 3 as the starting index.
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> gas = [2,3,4], cost = [3,4,3]
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<strong>Output:</strong> -1
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<strong>Explanation:</strong>
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You can't start at station 0 or 1, as there is not enough gas to travel to the next station.
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Let's start at station 2 and fill up with 4 unit of gas. Your tank = 0 + 4 = 4
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Travel to station 0. Your tank = 4 - 3 + 2 = 3
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Travel to station 1. Your tank = 3 - 3 + 3 = 3
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You cannot travel back to station 2, as it requires 4 unit of gas but you only have 3.
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Therefore, you can't travel around the circuit once no matter where you start.
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>n == gas.length == cost.length</code></li>
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<li><code>1 <= n <= 10<sup>5</sup></code></li>
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<li><code>0 <= gas[i], cost[i] <= 10<sup>4</sup></code></li>
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</ul>
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