What is the reason behind the segmentation fault?

Question

I'm unable to debug the following code in any debugger as it shows, "During startup program ended with segmentation fault SIGEGV"

This is code to find whether is a Graph is Bipartite or Not.

#include <stdlib.h>
#define ll long long

ll queue[1000000000];
ll last=0;
ll top=0;

int qempty()
{
    if(top==last) return 1;
    else return 0;
}

void emptyq()
{
    top=0;
    last=0;
}
void enqueue(long long x)
{
    queue[top++] = x;
}
void dequeue()
{
    queue[last++];
}

Here I defined the queue. And the following are the functions for Graph.

struct node
{
    ll vertex;
    struct node* next;
};

struct node* createNode(ll v)
{
    struct node *newnode = malloc(sizeof(struct node));
    newnode->vertex = v;
    newnode->next = NULL;
    return newnode;
}

struct Graph
{
    ll numVertices;
    struct node** adjLists;
};

struct Graph *createG (ll vertices)
{
    struct Graph *G = malloc(sizeof(struct Graph));
    G->numVertices = vertices;
    G->adjLists = malloc(vertices*sizeof(struct node*));
    for(int i=0;i<vertices;i++) G->adjLists[i]=NULL;
    return G;
}

void add(struct Graph* G, ll src, ll dest)
{
    struct node* newnode = createNode(dest);
    newnode->next = G->adjLists[src];
    G->adjLists[src] = newnode;

    newnode = createNode(src);
    newnode->next = G->adjLists[dest];
    G->adjLists[dest] = newnode;

}

This is the function for checking the edges between same layer of Breadth First Search.

ll BU(struct Graph *G, ll src, ll *color)
{ 
    color[src] = 1;
    emptyq();
    enqueue(src);
    while (qempty); 
    { 
        ll u = queue[last];
        dequeue;
        struct node *y = G->adjLists[u];
        while(y)
        { 
            if(color[y->vertex]==-1)
            { 
                color[y->vertex] = 1-color[u]; 
                enqueue(y->vertex);
            } 
            else if (color[y->vertex] == color[u]) return 0;

            y=y->next;
        }
    } 
    return 1; 

}

ll B(struct Graph *G) 
{ 
    ll x = G->numVertices;
    ll *color = malloc(x*sizeof(long long));
    for (ll i = 0; i < x; ++i) color[i] = -1; 

    for (ll i = 0; i < x; i++) 
    if (color[i] == -1) 
        if (BU(G,i,color)==0) 
        return 0; 

    else  return 1; 
} 

这是主要功能。我在main函数的第一行添加了一个断点，但是它拒绝继续。

int main()
{
    ll t;
    scanf("%lld",&t);
    printf("%lld",t);
    while(t--)
    {
        ll V,E;
        scanf("%lld %lld",&V,&E);
        printf("%lld %lld",V,E);
        struct Graph *G = createG(V);
        while(E--)
        {
            ll x,y;
            scanf("%lld %lld",&x,&y);
            add(G,x,y);
        }
        if(B(G)==1) printf("Yes\n");
        else printf("No\n");

    }
    return 0;
}

Answer 1

您可能要减小此尺寸：

ll queue[1000000000];

说到一个更合理的值1024。