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39 lines
1.8 KiB
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39 lines
1.8 KiB
HTML
<p>At a lemonade stand, each lemonade costs <code>$5</code>. Customers are standing in a queue to buy from you and order one at a time (in the order specified by bills). Each customer will only buy one lemonade and pay with either a <code>$5</code>, <code>$10</code>, or <code>$20</code> bill. You must provide the correct change to each customer so that the net transaction is that the customer pays <code>$5</code>.</p>
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<p>Note that you do not have any change in hand at first.</p>
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<p>Given an integer array <code>bills</code> where <code>bills[i]</code> is the bill the <code>i<sup>th</sup></code> customer pays, return <code>true</code> <em>if you can provide every customer with the correct change, or</em> <code>false</code> <em>otherwise</em>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> bills = [5,5,5,10,20]
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<strong>Output:</strong> true
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<strong>Explanation:</strong>
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From the first 3 customers, we collect three $5 bills in order.
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From the fourth customer, we collect a $10 bill and give back a $5.
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From the fifth customer, we give a $10 bill and a $5 bill.
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Since all customers got correct change, we output true.
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</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> bills = [5,5,10,10,20]
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<strong>Output:</strong> false
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<strong>Explanation:</strong>
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From the first two customers in order, we collect two $5 bills.
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For the next two customers in order, we collect a $10 bill and give back a $5 bill.
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For the last customer, we can not give the change of $15 back because we only have two $10 bills.
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Since not every customer received the correct change, the answer is false.
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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>1 <= bills.length <= 10<sup>5</sup></code></li>
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<li><code>bills[i]</code> is either <code>5</code>, <code>10</code>, or <code>20</code>.</li>
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</ul>
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