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Solution.java
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/**
* @author Oleg Cherednik
* @since 18.01.2019
*/
public class Solution {
public static void main(String... args) {
print(swapEveryTwoNodes(createList()));
print(swapEveryTwoNodes(createList(1)));
print(swapEveryTwoNodes(createList(1, 2)));
print(swapEveryTwoNodes(createList(1, 2, 3)));
print(swapEveryTwoNodes(createList(1, 2, 3, 4)));
print(swapEveryTwoNodes(createList(1, 2, 3, 4, 5)));
}
private static Node createList(int... arr) {
Node root = null;
Node prv = null;
for (int val : arr) {
Node node = new Node(val);
if (prv != null)
prv.next = node;
prv = node;
root = root != null ? root : node;
}
return root;
}
private static void print(Node node) {
boolean arrow = false;
while (node != null) {
if (arrow)
System.out.print(" -> ");
System.out.print(node.val);
node = node.next;
arrow = true;
}
System.out.println("\n---");
}
public static Node swapEveryTwoNodes(Node node) {
Node newRoot = null;
Node odd = null;
Node tail = null;
while (node != null) {
Node next = node.next;
if (odd == null) {
odd = node;
odd.next = null;
} else {
if (tail == null) {
tail = node;
tail.next = odd;
tail = odd;
newRoot = node;
} else {
tail.next = node;
tail.next.next = odd;
tail = odd;
}
odd = null;
}
node = next;
}
if (odd != null) {
if (tail != null)
tail.next = odd;
else
newRoot = odd;
}
return newRoot;
}
private static final class Node {
private final int val;
private Node next;
public Node(int val) {
this.val = val;
}
@Override
public String toString() {
return String.valueOf(val);
}
}
}