Permutations by swapping: Difference between revisions
Add Dart implementation
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[2, 3, 0, 1] Sign: 1
[3, 2, 0, 1] Sign: -1
</pre>
=={{header|Dart}}==
{{trans|Java}}
<syntaxhighlight lang="Dart">
void main() {
List<int> array = List.generate(4, (i) => i);
HeapsAlgorithm algorithm = HeapsAlgorithm();
algorithm.recursive(array);
print('');
algorithm.loop(array);
}
class HeapsAlgorithm {
void recursive(List array) {
_recursive(array, array.length, true);
}
void _recursive(List array, int n, bool plus) {
if (n == 1) {
_output(array, plus);
} else {
for (int i = 0; i < n; i++) {
_recursive(array, n - 1, i == 0);
_swap(array, n % 2 == 0 ? i : 0, n - 1);
}
}
}
void _output(List array, bool plus) {
print(array.toString() + (plus ? ' +1' : ' -1'));
}
void _swap(List array, int a, int b) {
var temp = array[a];
array[a] = array[b];
array[b] = temp;
}
void loop(List array) {
_loop(array, array.length);
}
void _loop(List array, int n) {
List<int> c = List.filled(n, 0);
_output(array, true);
bool plus = false;
int i = 0;
while (i < n) {
if (c[i] < i) {
if (i % 2 == 0) {
_swap(array, 0, i);
} else {
_swap(array, c[i], i);
}
_output(array, plus);
plus = !plus;
c[i]++;
i = 0;
} else {
c[i] = 0;
i++;
}
}
}
}
</syntaxhighlight>
{{out}}
<pre>
[0, 1, 2, 3] +1
[1, 0, 2, 3] -1
[2, 0, 1, 3] +1
[0, 2, 1, 3] -1
[1, 2, 0, 3] +1
[2, 1, 0, 3] -1
[3, 1, 2, 0] +1
[1, 3, 2, 0] -1
[2, 3, 1, 0] +1
[3, 2, 1, 0] -1
[1, 2, 3, 0] +1
[2, 1, 3, 0] -1
[3, 0, 2, 1] +1
[0, 3, 2, 1] -1
[2, 3, 0, 1] +1
[3, 2, 0, 1] -1
[0, 2, 3, 1] +1
[2, 0, 3, 1] -1
[3, 0, 1, 2] +1
[0, 3, 1, 2] -1
[1, 3, 0, 2] +1
[3, 1, 0, 2] -1
[0, 1, 3, 2] +1
[1, 0, 3, 2] -1
[3, 0, 1, 2] +1
[0, 3, 1, 2] -1
[1, 3, 0, 2] +1
[3, 1, 0, 2] -1
[0, 1, 3, 2] +1
[1, 0, 3, 2] -1
[2, 0, 3, 1] +1
[0, 2, 3, 1] -1
[3, 2, 0, 1] +1
[2, 3, 0, 1] -1
[0, 3, 2, 1] +1
[3, 0, 2, 1] -1
[3, 1, 2, 0] +1
[1, 3, 2, 0] -1
[2, 3, 1, 0] +1
[3, 2, 1, 0] -1
[1, 2, 3, 0] +1
[2, 1, 3, 0] -1
[2, 1, 0, 3] +1
[1, 2, 0, 3] -1
[0, 2, 1, 3] +1
[2, 0, 1, 3] -1
[1, 0, 2, 3] +1
[0, 1, 2, 3] -1
</pre>
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