German Collegiate Programming Contest 2018​ 

 1 //   Coolest Ski Route
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 #include <string>
 6 #include <algorithm>
 7 #include <utility>
 8 #include <vector>
 9 #include <map>
10 #include <queue>
11 #include <stack>
12 #include <cstdlib>
13 #include <cmath>
14 typedef long long ll;
15 #define lowbit(x) (x&(-x))
16 #define ls l,m,rt<<1
17 #define rs m+1,r,rt<<1|1
18 using namespace std;
19 #define pi acos(-1)
20 typedef pair<int,int> P;
21 const int N=1100;
22 const int inf=0x3f3f3f3f;
23 int dis[N];
24 int n,m;
25 struct Node{
26     int to,w;
27     Node(){}
28     Node(int TO,int W){
29         to=TO;
30         w=W;
31     }
32 };
33 vector<Node>vec[N];
34 void bfs(){
35     priority_queue<P,vector<P>,less<P> >que;//队首元素为最长距离
36     for(int i=1;i<=n;i++){
37         que.push(P(0,i));//起初，只有自己到自己
38     }
39     while(!que.empty()){
40         P q=que.top();
41         que.pop();
42         int v=q.second;
43         if(dis[v]>q.first) continue;//比当前的还大，就不用继续往下找了
44         for(int i=0;i<vec[v].size();i++){
45             Node Nod=vec[v][i];
46             int t=Nod.to;
47             if(dis[t]<dis[v]+Nod.w){
48                 dis[t]=dis[v]+Nod.w;//不断更新dis[t]
49                 que.push(P(dis[t],t));
50             }
51         }
52     }
53 }
54 int  main()
55 {
56     scanf("%d%d",&n,&m);
57     int s,t,c;
58     for(int i=0;i<m;i++)
59     {
60         scanf("%d%d%d",&s,&t,&c);
61         vec[s].push_back(Node(t,c));//有向图
62     }
63     memset(dis,0,sizeof(dis));//要初始化为0
64     bfs();
65     int MAX=-inf;
66     for(int i=1;i<=n;i++){
67         MAX=max(MAX,dis[i]);//i为终点，dis[i]为到i的最大路径长度
68     }
69     printf("%d\n",MAX);
70     return 0;
71 }

 

 

 1 //   Coolest Ski Route 
 2 #include <bits/stdc++.h>
 3 #define ll long long
 4 using namespace std;
 5 const int N = 1e3+10;
 6 struct Node{
 7     int  to,w;
 8     Node(){}
 9     Node(int TO,int W){
10         to=TO;
11         w=W;
12     }
13 };
14 vector<Node> vs[N];
15 int d[N],in[N];
16 void dfs(int v) {
17     for(int i = 0; i < vs[v].size(); i ++) {
18         Node Nod =vs[v][i];
19         int u=Nod.to;
20         if(d[u] < d[v] + Nod.w ) {
21             d[u] = d[v] + Nod.w;
22             dfs(u);
23         }
24     }
25 }
26 int main() {
27     int n, m;
28     cin >> n >> m;
29     for(int i = 0; i < m; i ++) {
30         int u, v, w;
31         cin >> u >> v >> w;
32         vs[u].push_back(Node(v,w));
33         in[v]++;
34     }
35     for(int i = 1; i <= n; i ++) {
36         if(!in[i])//本题任意两点之间为单向
37         dfs(i);
38     }
39     int MAX = 0;
40     for(int i = 1; i <= n; i ++) MAX = max(MAX, d[i]);
41     printf("%d\n",MAX);
42     return 0;
43 }

 

posted on 2018-07-19 19:56  cltt  阅读(331)  评论(0)    收藏  举报

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