Improve minimum-deletions-to-make-string-balanced

[yamcodes]

Summary by CodeRabbit

• New Features

  • Added an optimized split-point algorithm approach for the string balancing problem.

• Bug Fixes

  • Completed previously unimplemented dynamic programming solution.

• Chores

  • Removed incomplete solution implementations.
  • Updated tests and documentation to reflect implementation changes.

[coderabbitai]

Walkthrough

The PR refactors the minimum deletions to make string balanced problem by implementing a split-point optimization approach, updating the main DP implementation, simplifying the primary Solution class, removing unimplemented placeholder methods, and updating corresponding documentation and tests.

Changes

Cohort / File(s)	Summary
Core Algorithm Implementations src/main/java/codes/yam/leetcode/minimumdeletionstomakestringbalanced/Solution.java, SolutionDp.java, SolutionSplitPoint.java	Solution.java simplified by collapsing DP table into single-variable optimization (minDel); SolutionDp.java replaced with full bottom-up DP implementation; new SolutionSplitPoint.java introduced with split-point O(n) approach.
Removed Unimplemented Stubs src/main/java/codes/yam/leetcode/minimumdeletionstomakestringbalanced/SolutionMemoized.java, SolutionRecursive.java	Deleted unimplemented placeholder classes that threw UnsupportedOperationException; cleanup of incomplete stub implementations.
Documentation and Tests src/main/java/codes/yam/leetcode/minimumdeletionstomakestringbalanced/package-info.java, src/test/java/codes/yam/leetcode/minimumdeletionstomakestringbalanced/SolutionSplitPointTest.java, SolutionRecursiveTest.java	Updated package documentation to remove Recursive/Memoized entries and add SolutionSplitPoint; renamed SolutionMemoizedTest to SolutionSplitPointTest and updated to test new implementation; deleted SolutionRecursiveTest.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~35 minutes

Possibly related PRs

• Refactor minimum deletions to use O(n) time #10: Modifies Solution.minimumDeletions with different O(n) strategy to replace previous approach.
• Improve minimum-deletions-to-make-string-balanced space complexity to O(1) #20: Implements identical code-level change replacing prefix/suffix DP with single-pass O(1)-space split-point solution.
• Implement minimum-deletions-to-make-string-balanced #8: Modifies the same minimumDeletions function, replacing O(n²) split-index solution with space-optimized variant.

Poem

🐰 A rabbit hops through code so neat,
Old stubs are gone, algorithms sweet!
Split-points guide the way so bright,
O(n) dance in morning light!
Hop, hop—balance achieved just right! ✨

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title references the problem being improved but lacks specificity about the actual changes made (removing unimplemented stubs, adding optimized solution, implementing DP).
Merge Conflict Detection	✅ Passed	✅ No merge conflicts detected when merging into main

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch improve-minimum-deletions-to-make-string-balanced

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In
`@src/main/java/codes/yam/leetcode/minimumdeletionstomakestringbalanced/SolutionDp.java`:
- Around line 21-32: The code in SolutionDp (the DP loop using n, dp and
s.charAt(0)) crashes on empty input because it unconditionally reads
s.charAt(0); fix by adding an early guard in the method (e.g., in the method
containing variables n, dp, bCount) that returns 0 if n == 0 before accessing
s.charAt(0) or allocating dp, or handle the empty case by setting dp and bCount
appropriately; ensure the guard is placed before the lines referencing
s.charAt(0), dp[0], or using n to allocate arrays.