2008-09-08 19:43:42 -06:00
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package Sort
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export type SortInterface interface {
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len() int;
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less(i, j int) bool;
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swap(i, j int);
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}
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func Pivot(data SortInterface, a, b int) int {
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// if we have at least 10 elements, find a better median
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// by selecting the median of 3 elements and putting it
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// at position a
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if b - a >= 10 {
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m0 := (a + b) / 2;
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m1 := a;
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m2 := b - 1;
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// bubble sort on 3 elements
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if data.less(m1, m0) { data.swap(m1, m0); }
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if data.less(m2, m1) { data.swap(m2, m1); }
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if data.less(m1, m0) { data.swap(m1, m0); }
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// "m0 <= m1 <= m2"
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}
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m := a;
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for i := a + 1; i < b; i++ {
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if data.less(i, a) {
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m++;
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data.swap(i, m);
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}
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}
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data.swap(a, m);
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return m;
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}
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func Quicksort(data SortInterface, a, b int) {
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if a + 1 < b {
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m := Pivot(data, a, b);
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Quicksort(data, 0, m);
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Quicksort(data, m + 1, b);
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}
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}
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export func Sort(data SortInterface) {
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Quicksort(data, 0, data.len());
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}
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export func IsSorted(data SortInterface) bool {
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n := data.len();
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for i := n - 1; i > 0; i-- {
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if data.less(i, i - 1) {
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return false;
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}
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}
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return true;
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}
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// Convenience types for common cases
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export type IntArray struct {
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data *[]int;
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}
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func (p *IntArray) len() int { return len(p.data); }
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func (p *IntArray) less(i, j int) bool { return p.data[i] < p.data[j]; }
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func (p *IntArray) swap(i, j int) { p.data[i], p.data[j] = p.data[j], p.data[i]; }
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export type FloatArray struct {
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data *[]float;
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}
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func (p *FloatArray) len() int { return len(p.data); }
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func (p *FloatArray) less(i, j int) bool { return p.data[i] < p.data[j]; }
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func (p *FloatArray) swap(i, j int) { p.data[i], p.data[j] = p.data[j], p.data[i]; }
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export type StringArray struct {
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data *[]string;
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}
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func (p *StringArray) len() int { return len(p.data); }
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func (p *StringArray) less(i, j int) bool { return p.data[i] < p.data[j]; }
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func (p *StringArray) swap(i, j int) { p.data[i], p.data[j] = p.data[j], p.data[i]; }
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2008-09-09 19:13:08 -06:00
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// Convenience wrappers for common cases
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export func SortInts(a *[]int) { Sort(&IntArray{a}); }
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export func SortFloats(a *[]float) { Sort(&FloatArray{a}); }
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export func SortStrings(a *[]string) { Sort(&StringArray{a}); }
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export func IntsAreSorted(a *[]int) bool { return IsSorted(&IntArray{a}); }
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export func FloatsAreSorted(a *[]float) bool { return IsSorted(&FloatArray{a}); }
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export func StringsAreSorted(a *[]string) bool { return IsSorted(&StringArray{a}); }
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