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https://github.com/golang/go
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123 lines
3.0 KiB
Go
123 lines
3.0 KiB
Go
/*
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of "The Computer Language Benchmarks Game" nor the
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name of "The Computer Language Shootout Benchmarks" nor the names of
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its contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* The Computer Language Benchmarks Game
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* http://shootout.alioth.debian.org/
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*
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* contributed by The Go Authors.
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* Based on fannkuch.c by Heiner Marxen
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*/
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package main
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import (
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"flag"
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"fmt"
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)
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var n = flag.Int("n", 7, "count")
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func fannkuch(n int) int {
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if n < 1 {
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return 0
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}
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n1 := n - 1
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perm := make([]int, n)
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perm1 := make([]int, n)
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count := make([]int, n)
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for i := 0; i < n; i++ {
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perm1[i] = i // initial (trivial) permutation
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}
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r := n
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didpr := 0
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flipsMax := 0
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for {
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if didpr < 30 {
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for i := 0; i < n; i++ {
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fmt.Printf("%d", 1+perm1[i])
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}
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fmt.Printf("\n")
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didpr++
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}
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for ; r != 1; r-- {
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count[r-1] = r
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}
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if perm1[0] != 0 && perm1[n1] != n1 {
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flips := 0
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for i := 1; i < n; i++ { // perm = perm1
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perm[i] = perm1[i]
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}
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k := perm1[0] // cache perm[0] in k
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for { // k!=0 ==> k>0
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for i, j := 1, k-1; i < j; i, j = i+1, j-1 {
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perm[i], perm[j] = perm[j], perm[i]
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}
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flips++
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// Now exchange k (caching perm[0]) and perm[k]... with care!
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j := perm[k]
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perm[k] = k
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k = j
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if k == 0 {
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break
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}
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}
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if flipsMax < flips {
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flipsMax = flips
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}
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}
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for ; r < n; r++ {
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// rotate down perm[0..r] by one
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perm0 := perm1[0]
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for i := 0; i < r; i++ {
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perm1[i] = perm1[i+1]
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}
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perm1[r] = perm0
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count[r]--
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if count[r] > 0 {
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break
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}
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}
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if r == n {
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return flipsMax
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}
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}
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return 0
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}
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func main() {
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flag.Parse()
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fmt.Printf("Pfannkuchen(%d) = %d\n", *n, fannkuch(*n))
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}
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