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permutations.java
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131 lines (115 loc) · 4.13 KB
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/* Copyright (c) Jython Developers */
package org.python.modules.itertools;
import org.python.core.ArgParser;
import org.python.core.Py;
import org.python.core.PyIterator;
import org.python.core.PyObject;
import org.python.core.PyTuple;
import org.python.core.PyType;
import org.python.core.Visitproc;
import org.python.expose.ExposedMethod;
import org.python.expose.ExposedNew;
import org.python.expose.ExposedType;
@ExposedType(name = "itertools.permutations", base = PyObject.class, doc = permutations.permutations_doc)
public class permutations extends PyIterator {
public static final PyType TYPE = PyType.fromClass(permutations.class);
private PyIterator iter;
public static final String permutations_doc =
"permutations(iterable[, r]) --> permutations object\n\n" +
"Return successive r-length permutations of elements in the iterable.\n\n" +
"permutations(range(3), 2) --> (0,1), (0,2), (1,0), (1,2), (2,0), (2,1)";
public permutations() {
super();
}
public permutations(PyType subType) {
super(subType);
}
public permutations(PyObject iterable, int r) {
super();
permutations___init__(iterable, r);
}
@ExposedNew
@ExposedMethod
final void permutations___init__(PyObject[] args, String[] kwds) {
if (args.length > 2) {
throw Py.TypeError("permutations() takes at most 2 arguments (3 given)");
}
ArgParser ap = new ArgParser("permutations", args, kwds, "iterable", "r");
PyObject iterable = ap.getPyObject(0);
PyObject r = ap.getPyObject(1, Py.None);
int perm_length;
if (r == Py.None) {
perm_length = iterable.__len__();
}
else {
perm_length = r.asInt();
if (perm_length < 0) {
throw Py.ValueError("r must be non-negative");
}
}
permutations___init__(iterable, perm_length);
}
private void permutations___init__(final PyObject iterable, final int r) {
final PyTuple pool = PyTuple.fromIterable(iterable);
final int n = pool.__len__();
final int indices[] = new int[n];
for (int i = 0; i < n; i++) {
indices[i] = i;
}
final int cycles[] = new int[r];
for (int i = 0; i < r; i++) {
cycles[i] = n - i;
}
iter = new itertools.ItertoolsIterator() {
boolean firstthru = true;
@Override
public PyObject __iternext__() {
if (r > n) return null;
if (firstthru) {
firstthru = false;
return itertools.makeIndexedTuple(pool, indices, r);
}
for (int i = r - 1; i >= 0; i--) {
cycles[i] -= 1;
if (cycles[i] == 0) {
// rotate indices at the ith position
int first = indices[i];
for (int j = i; j < n - 1; j++) {
indices[j] = indices[j + 1];
}
indices[n - 1] = first;
cycles[i] = n - i;
} else {
int j = cycles[i];
int index = indices[i];
indices[i] = indices[n - j];
indices[n - j] = index;
return itertools.makeIndexedTuple(pool, indices, r);
}
}
return null;
}
};
}
public PyObject __iternext__() {
return iter.__iternext__();
}
@ExposedMethod
@Override
public PyObject next() {
return doNext(__iternext__());
}
/* Traverseproc implementation */
@Override
public int traverse(Visitproc visit, Object arg) {
int retVal = super.traverse(visit, arg);
if (retVal != 0) {
return retVal;
}
return iter != null ? visit.visit(iter, arg) : 0;
}
@Override
public boolean refersDirectlyTo(PyObject ob) {
return ob != null && (iter == ob || super.refersDirectlyTo(ob));
}
}