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Problem editorial
Implement Solution.calPoints, which evaluates a sequence of baseball scoring operations in the order given by operations. Maintain the scores that are currently recorded; an integer operation records that integer as a new score.
Baseball Game is a Stack Patterns problem, in the Simulation / Backtracking Helper subpattern. The pattern covers parentheses matching, monotonic stack, histogram, and expression evaluation
The reference solution runs in O(n), where n is the number of operations. time and O(n) for the stack of recorded scores. space.
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It explains the core insight, the complexity analysis and the common mistakes, with a worked solution.
Baseball Game is a Stack Patterns problem, in the Simulation / Backtracking Helper subpattern. Once the approach above makes sense, write it yourself and then work through the neighbouring problems that reuse it.