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			85 lines
		
	
	
		
			3.5 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
<p>You are keeping the scores for a baseball game with strange rules. At the beginning of the game, you start with an empty record.</p>
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<p>You are given a list of strings <code>operations</code>, where <code>operations[i]</code> is the <code>i<sup>th</sup></code> operation you must apply to the record and is one of the following:</p>
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<ul>
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	<li>An integer <code>x</code>.
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	<ul>
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		<li>Record a new score of <code>x</code>.</li>
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	</ul>
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	</li>
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	<li><code>'+'</code>.
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	<ul>
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		<li>Record a new score that is the sum of the previous two scores.</li>
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	</ul>
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	</li>
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	<li><code>'D'</code>.
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	<ul>
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		<li>Record a new score that is the double of the previous score.</li>
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	</ul>
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	</li>
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	<li><code>'C'</code>.
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	<ul>
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		<li>Invalidate the previous score, removing it from the record.</li>
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	</ul>
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	</li>
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</ul>
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<p>Return <em>the sum of all the scores on the record after applying all the operations</em>.</p>
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<p>The test cases are generated such that the answer and all intermediate calculations fit in a <strong>32-bit</strong> integer and that all operations are valid.</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> ops = ["5","2","C","D","+"]
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<strong>Output:</strong> 30
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<strong>Explanation:</strong>
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"5" - Add 5 to the record, record is now [5].
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"2" - Add 2 to the record, record is now [5, 2].
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"C" - Invalidate and remove the previous score, record is now [5].
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"D" - Add 2 * 5 = 10 to the record, record is now [5, 10].
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"+" - Add 5 + 10 = 15 to the record, record is now [5, 10, 15].
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The total sum is 5 + 10 + 15 = 30.
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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> ops = ["5","-2","4","C","D","9","+","+"]
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<strong>Output:</strong> 27
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<strong>Explanation:</strong>
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"5" - Add 5 to the record, record is now [5].
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"-2" - Add -2 to the record, record is now [5, -2].
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"4" - Add 4 to the record, record is now [5, -2, 4].
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"C" - Invalidate and remove the previous score, record is now [5, -2].
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"D" - Add 2 * -2 = -4 to the record, record is now [5, -2, -4].
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"9" - Add 9 to the record, record is now [5, -2, -4, 9].
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"+" - Add -4 + 9 = 5 to the record, record is now [5, -2, -4, 9, 5].
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"+" - Add 9 + 5 = 14 to the record, record is now [5, -2, -4, 9, 5, 14].
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The total sum is 5 + -2 + -4 + 9 + 5 + 14 = 27.
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> ops = ["1","C"]
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<strong>Output:</strong> 0
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<strong>Explanation:</strong>
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"1" - Add 1 to the record, record is now [1].
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"C" - Invalidate and remove the previous score, record is now [].
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Since the record is empty, the total sum is 0.
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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 <= operations.length <= 1000</code></li>
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	<li><code>operations[i]</code> is <code>"C"</code>, <code>"D"</code>, <code>"+"</code>, or a string representing an integer in the range <code>[-3 * 10<sup>4</sup>, 3 * 10<sup>4</sup>]</code>.</li>
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	<li>For operation <code>"+"</code>, there will always be at least two previous scores on the record.</li>
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	<li>For operations <code>"C"</code> and <code>"D"</code>, there will always be at least one previous score on the record.</li>
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</ul>
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