View Code of Problem 1070

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

const int N=100000;
int n,m;
int head[N];
struct Node
{
    int v,w,next;
}edge[N];

int cnt=0;
void addedge(int u,int v,int w)
{
    edge[cnt].v=v;
    edge[cnt].w=w;
    edge[cnt].next=head[u];
    head[u]=cnt++;
}

int vis[N];
int dis[N];
int q[N];
int res;

int bfs(int u)
{
    memset(vis,0,sizeof(vis));
    int front=0;
    int rear=1;
    q[1]=u;
    vis[u]=1;
    dis[u]=0;
    int ans=0;
    while(front < rear)
    {
        front++;
        int tmp = q[front];
        for(int i=head[tmp];i!=-1;i=edge[i].next)
        {
            int v=edge[i].v;
            if(!vis[v])
            {
                rear++;
                q[rear]=v;
                vis[v]=1;
                dis[v]=dis[tmp]+edge[i].w;
                if(dis[v]>ans)
                {
                    ans=dis[v];
                    res=v;
                }
            }
        }
    }
    return ans;
}

int main()
{
    int u,v,w;
    char ch;
    while(~scanf("%d%d",&n,&m))
    {
        memset(head,-1,sizeof(head));
        cnt=0;
        for(int i=0;i<m;i++)
        {
            scanf("%d %d %d %c",&u,&v,&w,&ch);
            addedge(u,v,w);
            addedge(v,u,w);
        }
        bfs(1);
        printf("%d\n",bfs(res));
   }
    return 0;
}