mirror of
https://github.com/rjNemo/underscore
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Ruidy
07d05425bb
Fixes useless capacity hint of 0 for map initialization. Uses estimated capacity of len(values)/10 to reduce map resizing operations. Changes: - Before: make(map[K][]V, 0) - capacity 0 is meaningless for maps - After: make(map[K][]V, len(values)/10) - reasonable estimate Impact: - Reduces map resizing overhead during population - Assumes ~10% unique keys (reasonable for grouping operations) - May over-allocate for high cardinality, but acceptable trade-off This is a minor optimization that avoids repeated map growth when keys are added. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
15 lines
365 B
Go
15 lines
365 B
Go
package underscore
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// GroupBy splits a slice into a map[K][]V grouped by the result of the iterator function.
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func GroupBy[K comparable, V any](values []V, f func(V) K) map[K][]V {
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res := make(map[K][]V, len(values)/10)
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for _, v := range values {
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k := f(v)
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if r, ok := res[k]; ok {
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res[k] = append(r, v)
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} else {
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res[k] = []V{v}
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}
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}
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return res
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}
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