German Collegiate Programming Contest 2018​

 //   Coolest Ski Route
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <string>
 #include <algorithm>
 #include <utility>
 #include <vector>
 #include <map>
 #include <queue>
 #include <stack>
 #include <cstdlib>
 #include <cmath>
 typedef long long ll;
 #define lowbit(x) (x&(-x))
 #define ls l,m,rt<<1
 #define rs m+1,r,rt<<1|1
 using namespace std;
 #define pi acos(-1)
 typedef pair<int,int> P;
 const int N=;
 const int inf=0x3f3f3f3f;
 int dis[N];
 int n,m;
 struct Node{
     int to,w;
     Node(){}
     Node(int TO,int W){
         to=TO;
         w=W;
     }
 };
 vector<Node>vec[N];
 void bfs(){
     priority_queue<P,vector<P>,less<P> >que;//队首元素为最长距离
     for(int i=;i<=n;i++){
         que.push(P(,i));//起初，只有自己到自己
     }
     while(!que.empty()){
         P q=que.top();
         que.pop();
         int v=q.second;
         if(dis[v]>q.first) continue;//比当前的还大，就不用继续往下找了
         for(int i=;i<vec[v].size();i++){
             Node Nod=vec[v][i];
             int t=Nod.to;
             if(dis[t]<dis[v]+Nod.w){
                 dis[t]=dis[v]+Nod.w;//不断更新dis[t]
                 que.push(P(dis[t],t));
             }
         }
     }
 }
 int  main()
 {
     scanf("%d%d",&n,&m);
     int s,t,c;
     for(int i=;i<m;i++)
     {
         scanf("%d%d%d",&s,&t,&c);
         vec[s].push_back(Node(t,c));//有向图
     }
     memset(dis,,sizeof(dis));//要初始化为0
     bfs();
     int MAX=-inf;
     for(int i=;i<=n;i++){
         MAX=max(MAX,dis[i]);//i为终点，dis[i]为到i的最大路径长度
     }
     printf("%d\n",MAX);
     return ;
 }

 //   Coolest Ski Route
 #include <bits/stdc++.h>
 #define ll long long
 using namespace std;
 const int N = 1e3+;
 struct Node{
     int  to,w;
     Node(){}
     Node(int TO,int W){
         to=TO;
         w=W;
     }
 };
 vector<Node> vs[N];
 int d[N],in[N];
 void dfs(int v) {
     for(int i = ; i < vs[v].size(); i ++) {
         Node Nod =vs[v][i];
         int u=Nod.to;
         if(d[u] < d[v] + Nod.w ) {
             d[u] = d[v] + Nod.w;
             dfs(u);
         }
     }
 }
 int main() {
     int n, m;
     cin >> n >> m;
     for(int i = ; i < m; i ++) {
         int u, v, w;
         cin >> u >> v >> w;
         vs[u].push_back(Node(v,w));
         in[v]++;
     }
     for(int i = ; i <= n; i ++) {
         if(!in[i])//本题任意两点之间为单向
         dfs(i);
     }
     int MAX = ;
     for(int i = ; i <= n; i ++) MAX = max(MAX, d[i]);
     printf("%d\n",MAX);
     return ;
 }