View Code of Problem 1070

/*
POJ:1985 Cow Marathon
2014/10/12/21:18
Yougth*/
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;
const int N = 44000;
struct Node
{
    int to,cap;
};
vector<Node> v[N];
int vis[N],dis[N];
int ans;
int BFS(int x)
{
    memset(dis,0,sizeof(dis));
    memset(vis,0,sizeof(vis));
    queue<int> q;
    q.push(x);
    vis[x]=1;
    int point = 0;
    while(!q.empty())
    {
        int f=q.front();
        q.pop();
        if(dis[f]>ans)
        {
            ans = dis[f];
            point = f;
        }
        for(int i=0;i<v[f].size();i++)
        {
            Node tmp = v[f][i];
            if(vis[tmp.to]==0)
            {
                vis[tmp.to]=1;
                dis[tmp.to] = dis[f] + tmp.cap;
                q.push(tmp.to);
            }
        }
    }
    return point;
}
int main()
{
    int n,m;
    while(~scanf("%d%d",&n,&m))
    {
        for(int i=0;i<m;i++)
        {
            int x,y,z;
            char c;
            scanf("%d %d %d %c",&x,&y,&z,&c);
            v[x].push_back((Node){y,z});
            v[y].push_back((Node){x,z});
        }
        ans = 0;
        int point = BFS(1);
        ans = 0;
        BFS(point);
        printf("%d\n",ans);
        for(int i=0;i<=n;i++)
            v[i].clear();
    }
    return 0;
}