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=1100;
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=1;i<=n;i++){
        que.push(P(0,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=0;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=0;i<m;i++)
    {
        scanf("%d%d%d",&s,&t,&c);
        vec[s].push_back(Node(t,c));//有向图
    }
    memset(dis,0,sizeof(dis));//要初始化为0
    bfs();
    int MAX=-inf;
    for(int i=1;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 0;
}

 

 

//   Coolest Ski Route 
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int N = 1e3+10;
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 = 0; 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 = 0; i < m; i ++) {
        int u, v, w;
        cin >> u >> v >> w;
        vs[u].push_back(Node(v,w));
        in[v]++;
    }
    for(int i = 1; i <= n; i ++) {
        if(!in[i])//本题任意两点之间为单向
        dfs(i);
    }
    int MAX = 0;
    for(int i = 1; i <= n; i ++) MAX = max(MAX, d[i]);
    printf("%d\n",MAX);
    return 0;
}