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uucore: make Range::merge linear instead of quadratic #14359

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uucore: make Range::merge linear instead of quadratic #14359

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16 changes: 7 additions & 9 deletions src/uucore/src/lib/features/ranges.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -246,16 +246,14 @@ impl Range {
/// Is guaranteed to return only disjoint ranges in a sorted order.
pub fn merge(mut ranges: Vec<Self>) -> Vec<Self> {
ranges.sort();

// merge overlapping ranges
for i in 0..ranges.len() {
let j = i + 1;

while j < ranges.len() && ranges[j].low <= ranges[i].high {
let j_high = ranges.remove(j).high;
ranges[i].high = max(ranges[i].high, j_high);
ranges.dedup_by(|a, b| {

@anastygnome anastygnome Sep 5, 2026 •
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pub fn merge(mut ranges: Vec<Self>) -> Vec<Self> {
    ranges.sort_unstable_by_key(|r| r.low);
[...]
}

Is better for two reasons :

We don't need a stable sort because we merge values, unstable sort is always more efficient.
Secondly, because we use the derived Ord trait, we compare both ends when we only need compare the low one.

if a.low <= b.high {
b.high = max(b.high, a.high);
true
} else {
false
}
}
});
ranges
}
}
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