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// Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
// The Computer Language Benchmarks Game
// https://benchmarksgame-team.pages.debian.net/benchmarksgame/
// Ported from JavaScript contributed by Isaac Gouy.
// Description: Repeatedly access a tiny integer-sequence.
// @dart = 2.9
import "package:expect/expect.dart";
class FannkuchTest {
static fannkuch(n) {
var p = new List(n), q = new List(n), s = new List(n);
var sign = 1, maxflips = 0, sum = 0, m = n - 1;
for (var i = 0; i < n; i++) {
p[i] = i;
q[i] = i;
s[i] = i;
}
do {
// Copy and flip.
var q0 = p[0]; // Cache 0th element.
if (q0 != 0) {
for (var i = 1; i < n; i++) q[i] = p[i]; // Work on a copy.
var flips = 1;
do {
var qq = q[q0];
if (qq == 0) {
// ... until 0th element is 0.
sum += sign * flips;
if (flips > maxflips) maxflips = flips; // New maximum?
break;
}
q[q0] = q0;
if (q0 >= 3) {
var i = 1, j = q0 - 1, t;
do {
t = q[i];
q[i] = q[j];
q[j] = t;
i++;
j--;
} while (i < j);
}
q0 = qq;
flips++;
} while (true);
}
if (sign == 1) {
var t = p[1];
p[1] = p[0];
p[0] = t;
sign = -1; // Rotate 0<-1.
} else {
// Rotate 0<-1 and 0<-1<-2.
var t = p[1];
p[1] = p[2];
p[2] = t;
sign = 1;
for (var i = 2; i < n; i++) {
var sx = s[i];
if (sx != 0) {
s[i] = sx - 1;
break;
}
if (i == m) {
return [sum, maxflips];
}
s[i] = i;
// Rotate 0<-...<-i+1.
t = p[0];
for (var j = 0; j <= i; j++) {
p[j] = p[j + 1];
}
p[i + 1] = t;
}
}
} while (true);
}
static testMain() {
var n = 6;
var pf = fannkuch(n);
Expect.equals(49, pf[0]);
Expect.equals(10, pf[1]);
print("${pf[0]}\nPfannkuchen($n) = ${pf[1]}");
}
}
main() {
FannkuchTest.testMain();
}