<p>We study a geometric facility location problem under imprecision. Given <i>n</i> unit segments on the real line, each with one of <i>k</i> colors, the goal is to place a point on each segment such that the resulting <i>minimum color-spanning interval</i> is as large as possible. A minimum color-spanning interval is an interval of minimum size that contains at least one point from a given segment of each color. We prove that if the input segments are pairwise disjoint, the problem can be solved in <i>O</i>(<i>n</i>) time, even for segments of arbitrary length. For overlapping segments, the problem becomes much more difficult. Nevertheless, we show that it can be solved in <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(O(n \log ^2 n)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>O</mi> <mo stretchy="false">(</mo> <mi>n</mi> <msup> <mo>log</mo> <mn>2</mn> </msup> <mi>n</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> time when <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(k=2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>k</mi> <mo>=</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation>, by exploiting several structural properties of candidate solutions, combined with a number of advanced algorithmic techniques. Interestingly, this shows a sharp contrast with the 2-dimensional version of the problem, recently shown to be NP-hard.</p>

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Computing Largest Minimum Color-Spanning Intervals of Imprecise Points

  • Ankush Acharyya,
  • Vahideh Keikha,
  • Maria Saumell,
  • Rodrigo I. Silveira

摘要

We study a geometric facility location problem under imprecision. Given n unit segments on the real line, each with one of k colors, the goal is to place a point on each segment such that the resulting minimum color-spanning interval is as large as possible. A minimum color-spanning interval is an interval of minimum size that contains at least one point from a given segment of each color. We prove that if the input segments are pairwise disjoint, the problem can be solved in O(n) time, even for segments of arbitrary length. For overlapping segments, the problem becomes much more difficult. Nevertheless, we show that it can be solved in \(O(n \log ^2 n)\) O ( n log 2 n ) time when \(k=2\) k = 2 , by exploiting several structural properties of candidate solutions, combined with a number of advanced algorithmic techniques. Interestingly, this shows a sharp contrast with the 2-dimensional version of the problem, recently shown to be NP-hard.