Holy Grail Bellman-Ford

Posted 2021-03-24 wstong

Holy Grail

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int maxn = 305, maxm = 505;
 4 const int inf = 0x3f3f3f3f;
 5 struct edge {
 6     int v, w;
 7 };
 8 vector<edge> maps[maxn];
 9 int dis[maxn], n, m;
10 
11 bool BellmanFord(int s) {  // s为源点
12     fill(dis, dis+n, inf);
13     dis[s] = 0;
14     for (int i = 0; i < n-1; i++) {
15         for (int u = 0; u < n; u++) {
16             for (int j = 0; j < maps[u].size(); j++) {
17                 int v = maps[u][j].v;
18                 int w = maps[u][j].w;
19                 if (dis[u] + w < dis[v]) {
20                     dis[v] = dis[u] + w;
21                 }
22             }
23         }
24     }
25     for (int u = 0; u < n; u++) {
26         for (int j = 0; j < maps[u].size(); j++) {
27             int v = maps[u][j].v;
28             int w = maps[u][j].w;
29             if (dis[u] + w < dis[v])
30                 return false;
31         }
32     }
33     return true;
34 }
35 int main() {
36     int t; scanf("%d",&t);
37     while (t--) {
38         scanf("%d%d",&n,&m);
39         for (int i = 0; i < n; i++) maps[i].clear();
40 
41         for (int i = 1; i <= m; i++) {
42             int u, v, w; scanf("%d%d%d",&u,&v,&w);
43             maps[u].push_back(edge{v,w});
44         }
45         for (int i = 1; i <= 6; i++) {
46             int u, v; scanf("%d%d",&u,&v);
47             bool flag = BellmanFord(v);
48             printf("%d
",-dis[u]);
49 
50             //if (flag == false) continue;
51             maps[u].push_back(edge{v,-dis[u]});
52         }
53     }
54 }