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Update Itertools.java #4

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114 changes: 83 additions & 31 deletions src/Itertools.java
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Original file line number Diff line number Diff line change
Expand Up @@ -31,8 +31,14 @@ public static Iterable<Integer> count(int start) {
return count(start, 1);
}

public static <T> Iterable<T> cycle(List<T> list) {
public static <T> Iterable<T> cycle(Iterable<T> iterable) {
return () -> new Iterator<T>() {

Iterator<T> iterator = iterable.iterator();

List<T> list = new ArrayList<>();
iterator.forEachRemaining(list::add);
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@samagra14 samagra14 Apr 3, 2019

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@Nitish145 This is rather a bad implementation as you are not utilising the iterable you are just storing them in a separate list and working from there on which defeats the purpose of supporting the iterables in the first place.


int count = -1;

@Override
Expand Down Expand Up @@ -96,10 +102,16 @@ public T next() {
* @param <T>
* @return
*/
public static <T> Iterable<T> chain(List<T>... iterables) {
public static <T> Iterable<T> chain(Iterable<T>... iterables) {

Iterator<T> iterator = iterables.iterator();

List<T> list1 = new ArrayList<>();
iterator.forEachRemaining(list1::add);

int size = 0;
for (List<T> list :
iterables) {
list1) {
size += list.size();
}
int finalSize = size;
Expand All @@ -117,12 +129,12 @@ public boolean hasNext() {
@Override
public T next() {
int presentIterableIndex = counter - sizeTillNow;
while (presentIterableIndex >= iterables[iterableNo].size()) {
sizeTillNow += iterables[iterableNo].size();
while (presentIterableIndex >= list1[iterableNo].size()) {
sizeTillNow += list1[iterableNo].size();
presentIterableIndex = counter - sizeTillNow;
iterableNo++;
}
return iterables[iterableNo].get(presentIterableIndex);
return list1[iterableNo].get(presentIterableIndex);
}
};
}
Expand All @@ -133,21 +145,31 @@ public T next() {
* @param <T>
* @return
*/
public static <T> Iterable<T> compress(List<T> data, List<Boolean> selectors) {
public static <T> Iterable<T> compress(Iterable<T> data, Iterable<Boolean> selectors) {
return () -> new Iterator<T>() {

Iterator<T> iterator1 = data.iterator();
Iterator<T> iterator2 = selectors.iterator();

List<T> data1 = new ArrayList<>();
iterator1.forEachRemaining(data1::add);

List<T> selectors1 = new ArrayList<>();
iterator2.forEachRemaining(selectors1::add);

int index = -1;

@Override
public boolean hasNext() {
index++;
while (index < data.size() && !selectors.get(index))
while (index < data1.size() && !selectors1.get(index))
index++;
return index < data.size();
return index < data1.size();
}

@Override
public T next() {
return data.get(index);
return data1.get(index);
}
};
}
Expand All @@ -158,24 +180,30 @@ public T next() {
* @param <T>
* @return
*/
public static <T> Iterable<T> dropWhile(Predicate<T> pred, List<T> seq) {
public static <T> Iterable<T> dropWhile(Predicate<T> pred, Iterable<T> seq) {
return () -> new Iterator<T>() {

Iterator<T> iterator = seq.iterator();

List<T> list = new ArrayList<>();
iterator.forEachRemaining(list::add);

boolean next = false;
int index = -1;

@Override
public boolean hasNext() {
index++;
while (!next && index < seq.size() && pred.pred(seq.get(index))) {
while (!next && index < list.size() && pred.pred(list.get(index))) {
index++;
}
next = true;
return index < seq.size();
return index < list.size();
}

@Override
public T next() {
return seq.get(index);
return list.get(index);
}
};
}
Expand All @@ -186,67 +214,85 @@ public T next() {
* @param <T>
* @return
*/
public static <T> Iterable<T> ifilter(Predicate<T> predicate, List<T> list) {
public static <T> Iterable<T> ifilter(Predicate<T> predicate, Iterable<T> list) {
return () -> new Iterator<T>() {

Iterator<T> iterator = list.iterator();

List<T> list1 = new ArrayList<>();
iterator.forEachRemaining(list1::add);

int index = -1;

@Override
public boolean hasNext() {
index++;
while (index < list.size() && !predicate.pred(list.get(index)))
while (index < list1.size() && !predicate.pred(list1.get(index)))
index++;
return index < list.size();
return index < list1.size();
}

@Override
public T next() {
return list.get(index);
return list1.get(index);
}
};
}


public static <T> Iterable<T> ifilterfalse(Predicate<T> predicate, List<T> list) {
public static <T> Iterable<T> ifilterfalse(Predicate<T> predicate, Iterable<T> list) {
return () -> new Iterator<T>() {

Iterator<T> iterator = list.iterator();

List<T> list1 = new ArrayList<>();
iterator.forEachRemaining(list1::add);

int index = -1;

@Override
public boolean hasNext() {
index++;
while (index < list.size() && predicate.pred(list.get(index)))
while (index < list1.size() && predicate.pred(list1.get(index)))
index++;
return index < list.size();
return index < list1.size();
}

@Override
public T next() {
return list.get(index);
return list1.get(index);
}
};
}

public static <T> Iterable<T> islice(List<T> seq, int start, int stop, int step) {
public static <T> Iterable<T> islice(Iterable<T> seq, int start, int stop, int step) {
return () -> new Iterator<T>() {

Iterator<T> iterator = seq.iterator();

List<T> list = new ArrayList<>();
iterator.forEachRemaining(list::add);

int index = start - step;

@Override
public boolean hasNext() {
index += step;
return index < seq.size() && index < stop && index >= start;
return index < list.size() && index < stop && index >= start;
}

@Override
public T next() {
return seq.get(index);
return list.get(index);
}
};
}

public static <T> Iterable<T> islice(List<T> seq, int stop, int step) {
public static <T> Iterable<T> islice(Iterable<T> seq, int stop, int step) {
return islice(seq, 0, stop, step);
}

public static <T> Iterable<T> islice(List<T> seq, int stop) {
public static <T> Iterable<T> islice(Iterable<T> seq, int stop) {
return islice(seq, 0, stop, 1);
}

Expand All @@ -272,24 +318,30 @@ public U next() {
};
}

public static <T> Iterable<T> takeWhile(Predicate<T> pred, List<T> seq) {
public static <T> Iterable<T> takeWhile(Predicate<T> pred, Iterable<T> seq) {
return () -> new Iterator<T>() {

Iterator<T> iterator = seq.iterator();

List<T> list = new ArrayList<>();
iterator.forEachRemaining(list::add);

boolean next = false;
int index = -1;

@Override
public boolean hasNext() {
index++;
while (!next && index < seq.size() && !pred.pred(seq.get(index))) {
while (!next && index < seq.size() && !pred.pred(list.get(index))) {
index++;
}
next = true;
return index < seq.size();
return index < list.size();
}

@Override
public T next() {
return seq.get(index);
return list.get(index);
}
};
}
Expand Down