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