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49 lines
1.7 KiB
HTML
<p>You are given an integer array <code>cards</code> of length <code>4</code>. You have four cards, each containing a number in the range <code>[1, 9]</code>. You should arrange the numbers on these cards in a mathematical expression using the operators <code>['+', '-', '*', '/']</code> and the parentheses <code>'('</code> and <code>')'</code> to get the value 24.</p>
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<p>You are restricted with the following rules:</p>
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<ul>
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<li>The division operator <code>'/'</code> represents real division, not integer division.
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<ul>
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<li>For example, <code>4 / (1 - 2 / 3) = 4 / (1 / 3) = 12</code>.</li>
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</ul>
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</li>
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<li>Every operation done is between two numbers. In particular, we cannot use <code>'-'</code> as a unary operator.
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<ul>
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<li>For example, if <code>cards = [1, 1, 1, 1]</code>, the expression <code>"-1 - 1 - 1 - 1"</code> is <strong>not allowed</strong>.</li>
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</ul>
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</li>
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<li>You cannot concatenate numbers together
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<ul>
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<li>For example, if <code>cards = [1, 2, 1, 2]</code>, the expression <code>"12 + 12"</code> is not valid.</li>
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</ul>
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</li>
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</ul>
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<p>Return <code>true</code> if you can get such expression that evaluates to <code>24</code>, and <code>false</code> otherwise.</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> cards = [4,1,8,7]
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<strong>Output:</strong> true
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<strong>Explanation:</strong> (8-4) * (7-1) = 24
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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> cards = [1,2,1,2]
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<strong>Output:</strong> 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>cards.length == 4</code></li>
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<li><code>1 <= cards[i] <= 9</code></li>
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</ul>
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