HDU 1874 畅通工程续

求任意两点间的最短距离 若不连通  输出-1

#include<cstdio>
#include<cstring>
#include<cstdlib>

using namespace std;

const int Max = 100000001;

struct N
{
    int v,w;
    N *next;
}*head[210];

void init(int n)
{
    for(int i = 0;i < n; i++)
    {
        head[i] = (struct N *)malloc(sizeof(struct N));
        head[i]->v = head[i]->w  = -1;
        head[i]->next = NULL;
    }
}

void link(int u,int v,int w)
{
    N *p1,*p2,*p;
    for(p1 = head[u],p2 = head[u]->next; p2 != NULL; p1 = p1->next,p2 = p2->next)
    {
        if(p2->v == v)
        {
            if(p2->w > w)
                p2->w = w;
            return;
        }
        if(p1->v < v && v < p2->v)
        {
            p = (struct N *)malloc(sizeof(struct N));
            p->v = v;
            p->w = w;
            p->next = p1->next;
            p1->next = p;
            return;
        }
    }
    p = (struct N *)malloc(sizeof(struct N));
    p->v = v;
    p->w = w;
    p->next = NULL;
    p1->next = p;
    return;
}

int mark[1000];

void find(int n,int start)
{
    int q[10001],t;
    int s,e,i;
    for(i = 0;i < n; i++)
        mark[i] = Max;
    N *p;
    for(s = 0,e = 0,p = head[start]->next; p != NULL; p = p->next)
    {
        q[e++] = p->v;
        mark[p->v] = p->w;
    }
    while(s != e)
    {
        t = q[s];
        s++;
        for(p = head[t]->next; p != NULL; p = p->next)
        {
            if(mark[t] + p->w < mark[p->v])
            {
                mark[p->v] = mark[t] + p->w;
                q[e++] = p->v;
            }
        }
    }
}

int hash[210];

int f(int x)
{
    while(x != hash[x])
    {
        x = hash[x];
    }
    return x;
}

void merge(int u,int v)
{
    int fu = f(u);
    int fv = f(v);
    hash[fu] = fv;
}

int main()
{
    int n,m,i,u,v,w,s,t;
    while(scanf("%d %d",&n,&m) != EOF)
    {
        init(n);
        for(i = 0;i < n; i++)
        {
            hash[i]= i;
        }
        for(i = 0;i < m;i++)
        {
            scanf("%d %d %d",&u,&v,&w);
            link(v,u,w);
            link(u,v,w);
            merge(u,v);
        }
        scanf("%d %d",&s,&t);
        int fs = f(s);
        int ft = f(t);
        if(fs != ft) printf("-1\n");
        else
        {
            if(s == t)
                printf("0\n");
            else
            {
                find(n,s);
                printf("%d\n",mark[t]);
            }
        }
    }
    return 0;
}