异常引起的控制台不完全停止

为什么下面这个程序能出结果但控制台不停止，程序里面广度搜索那会报错 （VS里面运行的）

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
#define MAX_VERTEM_NUM 10 

typedef enum {
    DG, DN, UDG, UDN
}graghKind;
//digraph  DG有向图
//directed network  DN有向网
//undirected graph  UDG无向图
//undirected network  UDN无向网

typedef char vertemData;
int visited[MAX_VERTEM_NUM] = { 0 };//访问数组

/*邻接矩阵*/
typedef struct {
    vertemData vert[MAX_VERTEM_NUM];            //顶点向量
    int adj[MAX_VERTEM_NUM][MAX_VERTEM_NUM];    //邻接矩阵
    int vertNum, arcNum;                            //图的顶点数和弧数
    graghKind gragh;                            //图的类型
}adjMatrix;

/*队列结构*/
typedef struct QNode
{
    vertemData data;
    struct QNode* next;
}QNode;

typedef struct
{
    QNode* front, * rear;  //队头队尾指针 
}LinkQueue;

/*求顶点位置*/
int locateVertem(adjMatrix* G, vertemData v) {
    for (int j = 0; j < G->vertNum; j++)
    {
        if (G->vert[j] == v)
        {
            return j;
        }
    }
}

/*创建无向图*/
int creatUDG(adjMatrix* G) {
    int i, j, k, weight;
    vertemData v1, v2;
    printf("请输入图的顶点数和弧数：\n");
    scanf("%d %d", &G->vertNum, &G->arcNum);
    for (i = 0; i < G->vertNum; i++)
        for (j = 0; j < G->vertNum; j++)
            G->adj[i][j] = 0;
    for (i = 0; i < G->vertNum; i++)
    {
        printf("请输入图的顶点%d：\n", i);
        getchar();
        scanf("%c", &G->vert[i]);
    }
    for (k = 0; k < G->arcNum; k++) {
        printf("请输入弧%d的两个顶点：\n", k);
        getchar();
        scanf("%c %c", &v1, &v2);
        i = locateVertem(G, v1);
        j = locateVertem(G, v2);
        G->adj[i][j] = 1;
        G->adj[j][i] = 1;
    }
    printf("\n无向图存储完毕！\n\n");
    return 0;
}

/*创建空队列*/
int init_queue(LinkQueue* L)
{
    L->front = L->rear = (QNode*)malloc(sizeof(QNode));
    if (!L->front) return 0;
    L->front->next = NULL;
    return 0;
}

/*判断队列是否为空*/
int empty_queue(LinkQueue* L)
{
    if (L->front->next == NULL) return 1;
    else return 0;
}

/*入队列*/
int in_queue(LinkQueue* L, int n)
{
    QNode* t = (QNode*)malloc(sizeof(QNode));
    if (!t) exit(0);
    t->data = n;
    t->next = NULL;
    L->rear->next = t;
    L->rear = t;
    free(t);
    return 0;
}

/*出队列*/
int out_queue(LinkQueue* L)
{
    QNode* t;
    if (L->front == L->rear) return 0;
    t = L->front->next;
    L->front->next = t->next;
    if (t == L->rear) L->rear = L->front;
    return 1;
}

//深度遍历无向图
void depth_first_traversal_UDG(adjMatrix* G, int* v, int n)
{
    int i;
    if (G == NULL) return;
    if (n<0 || n>G->vertNum) return;
    v[n] = 1;
    if (n == 0) printf("%c", G->vert[n]);
    else printf("->%c", G->vert[n]);
    for (i = 0; i < G->vertNum; i++)
        if (G->adj[n][i] != 0 && v[i] != 1) depth_first_traversal_UDG(G, v, i);
}

/*广度遍历*/
int BFS_traverse_UDN(adjMatrix* G)
{
    int i = 0, j;
    LinkQueue* L = (LinkQueue*)malloc(sizeof(LinkQueue));
    init_queue(L);
    printf("广度遍历无向图：");
    visited[i] = 1;
    printf("%c", G->vert[i]);
    in_queue(L, i);
    do
    {
        out_queue(L);
        for (j = 0; j < G->vertNum; j++)
        {
            if (G->adj[i][j] != 0 && visited[j] != 1)
            {
                visited[j] = 1;
                printf("->%c", G->vert[j]);
                in_queue(L, j);
            }
        }
        i++;
    } while (!empty_queue(L));
    free(L);
    return 0;
}

int main()
{
    adjMatrix* G = (adjMatrix*)malloc(sizeof(adjMatrix));
    creatUDG(G);
    int visited[300] = { 0 };
    printf("深度优先遍历无向图：\n");
    depth_first_traversal_UDG(G, visited, 0);
    BFS_traverse_UDN(G);
    return 0;
}