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< 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 >
< li > An integer < code > x< / code > .
< ul >
< li > Record a new score of < code > x< / code > .< / li >
< / ul >
< / li >
< li > < code > ' +' < / code > .
< ul >
< li > Record a new score that is the sum of the previous two scores.< / li >
< / ul >
< / li >
< li > < code > ' D' < / code > .
< ul >
< li > Record a new score that is the double of the previous score.< / li >
< / ul >
< / li >
< li > < code > ' C' < / code > .
< ul >
< li > Invalidate the previous score, removing it from the record.< / li >
< / ul >
< / li >
< / ul >
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< p > Return < em > the sum of all the scores on the record after applying all the operations< / em > .< / p >
< 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 >
< strong > Input:< / strong > ops = [" 5" ," 2" ," C" ," D" ," +" ]
< strong > Output:< / strong > 30
< strong > Explanation:< / strong >
" 5" - Add 5 to the record, record is now [5].
" 2" - Add 2 to the record, record is now [5, 2].
" C" - Invalidate and remove the previous score, record is now [5].
" D" - Add 2 * 5 = 10 to the record, record is now [5, 10].
" +" - Add 5 + 10 = 15 to the record, record is now [5, 10, 15].
The total sum is 5 + 10 + 15 = 30.
< / pre >
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< p > < strong class = "example" > Example 2:< / strong > < / p >
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< pre >
< strong > Input:< / strong > ops = [" 5" ," -2" ," 4" ," C" ," D" ," 9" ," +" ," +" ]
< strong > Output:< / strong > 27
< strong > Explanation:< / strong >
" 5" - Add 5 to the record, record is now [5].
" -2" - Add -2 to the record, record is now [5, -2].
" 4" - Add 4 to the record, record is now [5, -2, 4].
" C" - Invalidate and remove the previous score, record is now [5, -2].
" D" - Add 2 * -2 = -4 to the record, record is now [5, -2, -4].
" 9" - Add 9 to the record, record is now [5, -2, -4, 9].
" +" - Add -4 + 9 = 5 to the record, record is now [5, -2, -4, 9, 5].
" +" - Add 9 + 5 = 14 to the record, record is now [5, -2, -4, 9, 5, 14].
The total sum is 5 + -2 + -4 + 9 + 5 + 14 = 27.
< / 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" ]
< strong > Output:< / strong > 0
< strong > Explanation:< / strong >
" 1" - Add 1 to the record, record is now [1].
" C" - Invalidate and remove the previous score, record is now [].
Since the record is empty, the total sum is 0.
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< / pre >
< p > < / p >
< p > < strong > Constraints:< / strong > < / p >
< ul >
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< li > < code > 1 < = operations.length < = 1000< / code > < / li >
< 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 >
< li > For operations < code > " C" < / code > and < code > " D" < / code > , there will always be at least one previous score on the record.< / li >
< / ul >
