#include <stdio.h>
#include <stdlib.h>
typedef struct node_v {
int id;
struct node_v* prev;
struct node_v* next;
} Node_v;
typedef Node_v* Node;
void print(Node node) {
while (node->prev != NULL)
node = node->prev;
printf(" [%d]",node->id);
while (node->next != NULL) {
node = node->next;
printf("-[%d]",node->id);
}
printf("\n");
}
void connect(Node first,Node second) {
first->next = second;
second->prev = first;
}
Node createNode(int id) {
Node node = (Node)malloc(sizeof(Node_v));
node->id = id;
node->prev = NULL;
node->next = NULL;
return node;
}
int areTheyNeighbours(Node A,Node B) {
return ( A->next == B && B->prev == A ) || ( A->prev == B && B->next == A );
}
void refreshOuterPointers(Node A) {
if (A->prev != NULL)
A->prev->next = A;
if (A->next != NULL)
A->next->prev = A;
}
void swap(Node A,Node B) {
Node swapperVector[4];
swapperVector[0] = A->prev;
swapperVector[1] = B->prev;
swapperVector[2] = A->next;
swapperVector[3] = B->next;
if (areTheyNeighbours(A,B)) {
A->prev = swapperVector[2];
B->prev = swapperVector[0];
A->next = swapperVector[3];
B->next = swapperVector[1];
} else {
A->prev = swapperVector[1];
B->prev = swapperVector[0];
A->next = swapperVector[3];
B->next = swapperVector[2];
}
refreshOuterPointers(A);
refreshOuterPointers(B);
}
int main() {
Node n1 = createNode(1);
Node n2 = createNode(2);
Node n3 = createNode(3);
Node n4 = createNode(4);
connect(n1,n2);
connect(n2,n3);
connect(n3,n4);
printf("\nInitial state:");
print(n2);
printf("[1] <-> [2]: ");
swap(n1,n2);
print(n1);
printf("[2] <-> [4]: ");
swap(n2,n4);
print(n4);
return 0;
}