Breadth First Search or BFS for a Graph - c

Question

Based on the BFS algorithm, I am required to write a function SD() to find the shortest distance from vertex $v$ to $w$, in an undirected graph. Vertices ranged from 1 to $|V|$. The distance is measured by the number of edges. If there is no path from $v$ to $w$, then -1 is returned. You may assume that the input graph is always valid (no duplicate or any invalid link, etc.). The function prototype is given as follows:
int SD (Graph G, int v, int w);
For the sample input and output below, my code outputs 1 instead of 2 and I don't know what I'm doing wrong, more like I don't know what I am doing at this point, help would be appreciated thank you! (Please refer to the int SD(Graph g, int v, int z) section of the code below).
#include <stdio.h>
#include <stdlib.h>
typedef struct _listnode
{
int vertex;
struct _listnode *next;
} ListNode;
typedef struct _graph{
int V;
int E;
int *visited;
int **matrix;
}Graph;
typedef ListNode QueueNode;
typedef struct _queue{
int size;
QueueNode *head;
QueueNode *tail;
} Queue;
int SD (Graph G, int v, int w);
void printGraphMatrix(Graph );
// You should not change the prototypes of these functions
void enqueue(Queue *qPtr, int item);
int dequeue(Queue *qPtr);
int getFront(Queue q);
int isEmptyQueue(Queue q);
void removeAllItemsFromQueue(Queue *qPtr);
int main()
{
Graph g;
int i,j;
printf("Enter the number of vertices:\n");
scanf("%d",&g.V);
g.E = 0;
g.matrix = (int **)malloc(g.V*sizeof(int *));
for(i=0;i<g.V;i++)
g.matrix[i] = (int *)malloc(g.V*sizeof(int));
for(i=0;i<g.V;i++)
for(j=0;j<g.V;j++)
g.matrix[i][j] = 0;
g.visited = (int *) malloc(sizeof(int)*g.V);
for(i=0;i<g.V;i++) g.visited[i] = 0;
int V1, V2;
printf("Enter two vertices which are adjacent to each other:\n");
while(scanf("%d %d",&V1,&V2)==2)
{
if(V1>0 && V1<=g.V && V2>0 && V2<=g.V)
{
g.matrix[V1-1][V2-1] = 1;
g.matrix[V2-1][V1-1] = 1;
g.E++;
}
else
break;
printf("Enter two vertices which are adjacent to each other: (press a to stop)\n");
}
scanf("%*c");
// printGraphMatrix(g);
printf("Enter two vertices for finding their shortest distance: (press a to stop)\n");
scanf("%d %d", &i, &j);
int d = SD(g,i,j);
if(d==-1)
printf("%d and %d are unconnected.\n",i,j);
else
printf("The shortest distance is %d\n",d);
return 0;
}
int SD(Graph g, int v, int z){
int * distance;
distance = (int *) malloc(sizeof(int)*g.V);
// Initialize distances
for(int i = 0; i < g.V; i++)
{
distance[i] = -1;
}
// queue to do BFS.
Queue q;
q.size = 0;
q.head = NULL;
q.tail = NULL;
int w;
int i;
enqueue(&q,v);
distance[v-1] = distance[v-1] + 1;
g.visited[v-1] = 1;
while(isEmptyQueue(q)==0){
w = dequeue(&q);
for(i=0;i<g.V;i++)
{
if(g.matrix[w-1][i] == 1 && g.visited[i]==0)
{
g.visited[i]=1;
distance[i] = distance[i] + 3;
enqueue(&q,i+1);
}
}
}
if(z <= g.V) return distance[z-1];
return -1;
}
void printGraphMatrix(Graph g)
{
int i,j;
for(i=0;i<g.V;i++){
for(j=0;j<g.V;j++)
printf("%d\t",g.matrix[i][j]);
printf("\n");
}
}
void enqueue(Queue *qPtr, int item) {
QueueNode *newNode;
newNode = malloc(sizeof(QueueNode));
if(newNode==NULL) exit(0);
newNode->vertex = item;
newNode->next = NULL;
if(isEmptyQueue(*qPtr))
qPtr->head=newNode;
else
qPtr->tail->next = newNode;
qPtr->tail = newNode;
qPtr->size++;
}
int dequeue(Queue *qPtr) {
if(qPtr==NULL || qPtr->head==NULL){ //Queue is empty or NULL pointer
return 0;
}
else{
int headValue = qPtr->head->vertex;
QueueNode *temp = qPtr->head;
qPtr->head = qPtr->head->next;
if(qPtr->head == NULL) //Queue is emptied
qPtr->tail = NULL;
free(temp);
qPtr->size--;
return headValue;
}
}
int getFront(Queue q){
return q.head->vertex;
}
int isEmptyQueue(Queue q) {
if(q.size==0) return 1;
else return 0;
}
void removeAllItemsFromQueue(Queue *qPtr)
{
while(dequeue(qPtr));
}