mirror of
https://github.com/golang/go
synced 2024-10-05 04:21:22 -06:00
839a68469b
TBR=r OCL=23121 CL=23127
168 lines
3.8 KiB
Go
168 lines
3.8 KiB
Go
// 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
|
|
|
|
type SortInterface interface {
|
|
Len() int;
|
|
Less(i, j int) bool;
|
|
Swap(i, j int);
|
|
}
|
|
|
|
func min(a, b int) int {
|
|
if a < b {
|
|
return a;
|
|
}
|
|
return b;
|
|
}
|
|
|
|
// Insertion sort
|
|
func insertionSort(data SortInterface, a, b int) {
|
|
for i := a+1; i < b; i++ {
|
|
for j := i; j > a && data.Less(j, j-1); j-- {
|
|
data.Swap(j, j-1);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Quicksort, following Bentley and McIlroy,
|
|
// ``Engineering a Sort Function,'' SP&E November 1993.
|
|
|
|
// Move the median of the three values data[a], data[b], data[c] into data[a].
|
|
func medianOfThree(data SortInterface, a, b, c int) {
|
|
m0 := b;
|
|
m1 := a;
|
|
m2 := c;
|
|
// 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); }
|
|
// now data[m0] <= data[m1] <= data[m2]
|
|
}
|
|
|
|
func swapRange(data SortInterface, a, b, n int) {
|
|
for i := 0; i < n; i++ {
|
|
data.Swap(a+i, b+i);
|
|
}
|
|
}
|
|
|
|
func doPivot(data SortInterface, lo, hi int) (midlo, midhi int) {
|
|
m := (lo+hi)/2;
|
|
if hi - lo > 40 {
|
|
// Tukey's ``Ninther,'' median of three medians of three.
|
|
s := (hi - lo) / 8;
|
|
medianOfThree(data, lo, lo+s, lo+2*s);
|
|
medianOfThree(data, m, m-s, m+s);
|
|
medianOfThree(data, hi-1, hi-1-s, hi-1-2*s);
|
|
}
|
|
medianOfThree(data, lo, m, hi-1);
|
|
|
|
// Invariants are:
|
|
// data[lo] = pivot (set up by ChoosePivot)
|
|
// data[lo <= i < a] = pivot
|
|
// data[a <= i < b] < pivot
|
|
// data[b <= i < c] is unexamined
|
|
// data[c <= i < d] > pivot
|
|
// data[d <= i < hi] = pivot
|
|
//
|
|
// Once b meets c, can swap the "= pivot" sections
|
|
// into the middle of the array.
|
|
pivot := lo;
|
|
a, b, c, d := lo+1, lo+1, hi, hi;
|
|
for b < c {
|
|
if data.Less(b, pivot) { // data[b] < pivot
|
|
b++;
|
|
continue;
|
|
}
|
|
if !data.Less(pivot, b) { // data[b] = pivot
|
|
data.Swap(a, b);
|
|
a++;
|
|
b++;
|
|
continue;
|
|
}
|
|
if data.Less(pivot, c-1) { // data[c-1] > pivot
|
|
c--;
|
|
continue;
|
|
}
|
|
if !data.Less(c-1, pivot) { // data[c-1] = pivot
|
|
data.Swap(c-1, d-1);
|
|
c--;
|
|
d--;
|
|
continue;
|
|
}
|
|
// data[b] > pivot; data[c-1] < pivot
|
|
data.Swap(b, c-1);
|
|
b++;
|
|
c--;
|
|
}
|
|
|
|
n := min(b-a, a-lo);
|
|
swapRange(data, lo, b-n, n);
|
|
|
|
n = min(hi-d, d-c);
|
|
swapRange(data, c, hi-n, n);
|
|
|
|
return lo+b-a, hi-(d-c);
|
|
}
|
|
|
|
func quickSort(data SortInterface, a, b int) {
|
|
if b - a > 7 {
|
|
mlo, mhi := doPivot(data, a, b);
|
|
quickSort(data, a, mlo);
|
|
quickSort(data, mhi, b);
|
|
} else if b - a > 1 {
|
|
insertionSort(data, a, b);
|
|
}
|
|
}
|
|
|
|
func Sort(data SortInterface) {
|
|
quickSort(data, 0, data.Len());
|
|
}
|
|
|
|
|
|
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
|
|
|
|
type IntArray []int
|
|
|
|
func (p IntArray) Len() int { return len(p); }
|
|
func (p IntArray) Less(i, j int) bool { return p[i] < p[j]; }
|
|
func (p IntArray) Swap(i, j int) { p[i], p[j] = p[j], p[i]; }
|
|
|
|
|
|
type FloatArray []float
|
|
|
|
func (p FloatArray) Len() int { return len(p); }
|
|
func (p FloatArray) Less(i, j int) bool { return p[i] < p[j]; }
|
|
func (p FloatArray) Swap(i, j int) { p[i], p[j] = p[j], p[i]; }
|
|
|
|
|
|
type StringArray []string
|
|
|
|
func (p StringArray) Len() int { return len(p); }
|
|
func (p StringArray) Less(i, j int) bool { return p[i] < p[j]; }
|
|
func (p StringArray) Swap(i, j int) { p[i], p[j] = p[j], p[i]; }
|
|
|
|
|
|
// Convenience wrappers for common cases
|
|
|
|
func SortInts(a []int) { Sort(IntArray(a)); }
|
|
func SortFloats(a []float) { Sort(FloatArray(a)); }
|
|
func SortStrings(a []string) { Sort(StringArray(a)); }
|
|
|
|
|
|
func IntsAreSorted(a []int) bool { return IsSorted(IntArray(a)); }
|
|
func FloatsAreSorted(a []float) bool { return IsSorted(FloatArray(a)); }
|
|
func StringsAreSorted(a []string) bool { return IsSorted(StringArray(a)); }
|