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Cursor - Implement RichIterator and Extra APIs. #13

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13 changes: 6 additions & 7 deletions src/main/java/iterator/Extra.java
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ private Extra() {
* @implNote try implement it with only one line of code !
*/
public static int sumAges(RichIterator<Person> itr) {
throw new NotImplementedException();
return itr.foldLeft(0, (sum, person) -> sum + person.age);
}

/**
Expand All @@ -22,7 +22,7 @@ public static int sumAges(RichIterator<Person> itr) {
* @implNote try implement it with only one line of code !
*/
public static Optional<Integer> avgAge(RichIterator<Person> itr) {
throw new NotImplementedException();
return Optional.of(itr.foldLeft(Pair.apply(0, 0), (acc, p) -> Pair.apply(acc._1 + p.age, acc._2 + 1))).filter(acc -> acc._2 > 0).map(acc -> acc._1 / acc._2);
}

/**
Expand All @@ -40,8 +40,7 @@ public static Optional<Integer> avgAge(RichIterator<Person> itr) {
* @implNote try implement it with only one line of code !
*/
public static <A, B> RichIterator<Pair<A, B>> product(Iterable<A> a, Iterable<B> b) {
// TODO: implement this method
throw new NotImplementedException();
return RichIterator.from(a).flatMap(x -> RichIterator.from(b).map(y -> Pair.apply(x, y)));
}

/**
Expand All @@ -50,7 +49,8 @@ public static <A, B> RichIterator<Pair<A, B>> product(Iterable<A> a, Iterable<B>
* @implNote try implement it with only 2 lines of code !
*/
public static RichIterator<Integer> multiplicationBoard() {
throw new NotImplementedException();
Iterable<Integer> range = () -> RichIterator.iterate(1, i -> i + 1).take(10);
return product(range, range).map(p -> p._1 * p._2);
}

/**
Expand All @@ -62,8 +62,7 @@ public static RichIterator<Integer> multiplicationBoard() {
* @implNote try implement it with only one line of code !
*/
public static RichIterator<Integer> factorial() {
// TODO: implement this method
throw new NotImplementedException();
return RichIterator.iterate(1, x -> x + 1).scanLeft(1, (acc, n) -> acc * n);
}

public static class Person {
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