如何分别交错这两个链表？

Question

Im trying to interleave two lists such that:

list1 starts as {a1,a2,a3,a4,a5} list2 starts as {b1,b2,b3,b4,b5}

And I want them to be {a1,b2,a3,b4,a5} {b1,a2,b3,a4,b5}

This is my code:

public void interleave(A3LinkedList other) {
  A3Node thisCurrent = this.head;
  A3Node otherCurrent = other.head;
    int count = 1;
    while(count <= this.length){
        System.out.println("List1 current at loop "+ count + ": " + thisCurrent); // just to debug
        System.out.println("List2 current at loop "+ count + ": " + otherCurrent);

        A3Node tempThis = thisCurrent;
        A3Node tempOther = otherCurrent;

        //if(count%2 == 0){ //if count is even, aka every second object in list
            thisCurrent = tempOther; // makes thisCurrent same as otherCurrent
            otherCurrent = tempThis; // makes otherCurrent same as temp saved
        //}


        thisCurrent = thisCurrent.next;
        otherCurrent = otherCurrent.next;
        count ++;
    }
}

The output from the println methods in the while loop show me that the nodes are swapping correctly, but the end result in another tester program shows me that the lists arent changing at all.

Output from inside the while loop:

List1 current at loop 1: A
List2 current at loop 1: L
List1 current at loop 2: M
List2 current at loop 2: B
List1 current at loop 3: C
List2 current at loop 3: N
List1 current at loop 4: O
List2 current at loop 4: D
List1 current at loop 5: E
List2 current at loop 5: P
List1 current at loop 6: Q
List2 current at loop 6: F
List1 current at loop 7: G
List2 current at loop 7: R

Output from tester: {ABCDEFG} {LMNOPQR} Failed test: testInterleave at line 203 Failed test: testInterleave at line 204

As one can see, the tester output isn't what it should be, it isn't passing the test. Why?

Answer 1

Your code isn't working because you're creating local object references in the method and only reassigning those local references. You need to reassign the references' members (ie A3Node.next ) and what they point to. Like the following:

public void interleave(A3LinkedList other) {
        A3Node thisCurrent = this.head;
        A3Node otherCurrent = other.head;
        
        int count = 1;
        while(count <= this.length){
            // don't want to lose reference to other's next
            A3Node otherNext = otherCurrent.next;
            
            // now we change the references that next are pointing to
            
            // make otherCurrent.next point to thisCurrent.next
            otherCurrent.next = thisCurrent.next;
            // make thisCurrent.next point to otherNext.next (old otherCurrent.next)
            thisCurrent.next = otherNext;
            
            thisCurrent = thisCurrent.next;
            otherCurrent = otherCurrent.next;
            count += 1;
        }
    }