# fannkuch-redux Dart jit #2 program

## source code

```/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/

contributed by Jos Hirth
(previously used) warmup code suggested by Vyacheslav Egorov
transliterated from Isaac Gouy's C# program,
which was transliterated from Mike Pall's Lua program
+ null safety
*/

fannkuch(n) {
var p = List<int>.filled(n, 0),
q = List<int>.filled(n, 0),
s = List<int>.filled(n, 0);
int sign = 1, maxflips = 0, sum = 0, m = n - 1;
for (int 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 (int 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) {
int 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);
}
// Permute.
if (sign == 1) {
var t = p[1];
p[1] = p[0];
p[0] = t;
sign = -1; // Rotate 0<-1.
} else {
var t = p[1];
p[1] = p[2];
p[2] = t;
sign = 1; // Rotate 0<-1 and 0<-1<-2.
for (int i = 2; i < n; i++) {
var sx = s[i];
if (sx != 0) {
s[i] = sx - 1;
break;
}
if (i == m) return [sum, maxflips]; // Out of permutations.
s[i] = i;
// Rotate 0<-...<-i+1.
t = p[0];
for (int j = 0; j <= i; j++) {
p[j] = p[j + 1];
}
p[i + 1] = t;
}
}
} while (true);
}

void main(args) {
int n = args.length > 0 ? int.parse(args[0]) : 7;
var pf = fannkuch(n);
print("\${pf[0]}\nPfannkuchen(\$n) = \${pf[1]}");
}
```

## notes, command-line, and program output

```NOTES:
64-bit Ubuntu quad core
Dart SDK version: 3.4.1 (stable)
Tue May 21 15:46:25 2024

Tue, 28 May 2024 21:58:13 GMT

MAKE:
/opt/src/dart-sdk/bin/dart analyze
Analyzing tmp...
No issues found!

1.80s to complete and log all make actions

COMMAND LINE:
/opt/src/dart-sdk/bin/dart run  fannkuchredux.dartjit-2.dartjit 12

PROGRAM OUTPUT:
3968050
Pfannkuchen(12) = 65
```