Showing posts with label Merge 2 Sorted Linked Lists. Show all posts
Showing posts with label Merge 2 Sorted Linked Lists. Show all posts ## Merge 2 Sorted Linked Lists

Function that takes two lists, each of which is sorted in increasing order, and merges the two together into one list which is in increasing order. The new list should be made by splicing
together the nodes of the first two lists.
For example if the first linked list a is 5->10->15 and the other linked list b is 2->3->20, then SortedMerge() should return a pointer to the head node of the merged list 2->3->5->10->15->20.

There are many cases to deal with: either ‘a’ or ‘b’ may be empty, during processing either ‘a’ or ‘b’ may run out first, and finally there’s the problem of starting the result list empty, and building it up while going through ‘a’ and ‘b’.

```{ 3, 6, 7, 8, 9 }
{ 1, 5, 7, 10, 89 }
OUTPUT: 1, 3, 5, 6, 7, 7, 8, 9, 10, 89

{}
{3, 4, 7, 8}
OUTPUT: 3, 4, 7, 8
```
Lets see simple Java code to get merge 2 sorted linked list without creating new (3rd) linked list and only by splicing both list nodes.

```class NODE {

int data;
NODE next;

public NODE(int data) {
this.data = data;
this.next = null;
}
}

public static void main(String[] args) {

int val1[] = new int[] { 3, 6, 7, 8, 9 };
int val2[] = new int[] { 1, 5, 7, 10, 89 };

/* Create 1st linked list */

/* Create 2nd linked list */

NODE print = start;
while (print != null) {
System.out.println("----> " + print.data);
print = print.next;
}
}

/*
* Create linked list based on given array
*/
NODE start = null;
for (int i : val) {
NODE tmp = new NODE(i);
if (start == null) {
start = tmp;
} else {
NODE mover = start;
while (mover.next != null) {
mover = mover.next;
}
mover.next = tmp;
}
}
return start;
}

/*
*/
public NODE mergeLinkedList(NODE first, NODE second) {

if (first == null)
return second;
if (second == null)
return first;

NODE start = null;
NODE mover = null;

while (first != null && second != null) {
if (start == null) {
if (first.data <= second.data) {
start = mover = first;
first = first.next;
} else if (second.data <= first.data) {
start = mover = second;
second = second.next;
}
} else {
if (first.data <= second.data) {
mover.next = first;
first = first.next;
} else if (second.data <= first.data) {
mover.next = second;
second = second.next;
}
mover = mover.next;
}
}
if (first == null) {
while (second != null) {
mover.next = second;
second = second.next;
mover = mover.next;
}
}
if (second == null) {
while (first != null) {
mover.next = first;
first = first.next;
mover = mover.next;
}
}
return start;
}
}
```
OUTPUT:

```----> 1
----> 3
----> 5
----> 6
----> 7
----> 7
----> 8
----> 9
----> 10
----> 89
```