【临时】题目

【临时】题目

import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.Supplier;

class linkedList {
public T head;
public linkedList tail;

linkedList(T head) {
    this.head = head;
    this.tail = null;
}

linkedList(T head, linkedList tail) {
    this.head = head;
    this.tail = tail;
}

}

class Main {
public static linkedList cons(T head) {
return new linkedList(head);
}

public static  linkedList cons(T head, linkedList tail) {
    return new linkedList(head, tail);
}

public static  String listToString(linkedList list) {
    if (list == null) {
        return "";
    }

    if (list.tail == null) {
        return list.head.toString();
    }

    return list.head.toString() + " " + listToString(list.tail);
}

public static  linkedList myMap(Function fn, linkedList list) {
    if (list == null) {
        return null;
    }

    return cons(fn.apply(list.head), myMap(fn, list.tail));
}

public static  T2 myReduce(BiFunction fn, T2 accm, linkedList list) {
    if (list == null) {
        return accm;
    }

    return myReduce(fn, fn.apply(accm, list.head), list.tail);
}

public static  T2 myReduceRight(BiFunction fn, T2 accm, linkedList list) {
    // [BEGIN] YOUR CODE HERE
    return null;
    // [END] YOUR CODE HERE
}

 public static  linkedList myMap2(Function fn, linkedList list) {
     // [BEGIN] YOUR CODE HERE
     return null;
     // [END] YOUR CODE HERE
 }

public static void main(String[] args) {
    linkedList exampleList = cons(1, cons(2, cons(3, cons(4))));
    Function plusOne = (x) -> x + 1;
    BiFunction xTimesTwoPlusY = (x, y) -> x * 2 + y;
    BiFunction printXAndReturnY = (x, y) -> {
        System.out.println(x);
        return y;
    };
    Function toString = (x) -> x.toString();
    BiFunction unfoldCalculation = (x, y) -> "fn(" + x.toString() + ", " + y.toString() + ")";
    Function printAndReturn = (x) -> {
        System.out.println(x);
        return x;
    };
    System.out.println(listToString(exampleList) + " should be 1 2 3 4");
    System.out.println(listToString(myMap(plusOne, exampleList)) + " should be 2 3 4 5");
    System.out.println(myReduce(xTimesTwoPlusY, 0, exampleList) + " should be 26");
    System.out.println(myReduce(unfoldCalculation, "accm", myMap(toString, exampleList)) + " should be fn(fn(fn(fn(accm, 1), 2), 3), 4)");
    System.out.println(myReduceRight(xTimesTwoPlusY, 0, exampleList) + " should be 20");
    System.out.println(myReduceRight(unfoldCalculation, "accm", myMap(toString, exampleList)) + " should be fn(1, fn(2, fn(3, fn(4, accm))))");
    System.out.println("Below should output 4 3 2 1 each on a separate line:");
    myReduceRight(printXAndReturnY, 0, exampleList);
    System.out.println(listToString(myMap2(plusOne, exampleList)) + " should be 2 3 4 5");
    System.out.println("The two outputs below should be equal:");
    System.out.println("First output:");
    myMap(printAndReturn, exampleList);
    System.out.println("Second output:");
    myMap2(printAndReturn, exampleList);
}

}