【分层图最长路，spfa】P1073 最优贸易

  1 #include<iostream>
  2 #include<string>
  3 #include<queue>
  4 #include<stack>
  5 #include<vector>
  6 #include<map>
  7 #include<cstdio>
  8 #include<cstdlib>
  9 #include<algorithm>
 10 #include<set>
 11 #include<list>
 12 #include<iomanip>
 13 #include<cstring>
 14 #include<cmath>
 15 #include<limits>
 16 using namespace std;
 17 
 18 #define au auto
 19 #define debug(i) cout<<"<debug> "<<i<<" <\debug>"<<endl
 20 #define mfor(i,a,b) for(register int i=(a);i<=(b);i++)
 21 #define mrep(i,a,b) for(register int i=(a);i>=(b);i--)
 22 #define LLL __int128
 23 #define Re register
 24 #define il inline
 25 #define mem(a,b) memset(a,(b),sizeof(a))
 26 typedef pair<int, int> intpair;
 27 typedef pair<long long int, long long int> llpair;
 28 typedef long long int LL;
 29 const int INF = 0x3f3f3f3f;
 30 const long long int INFLL = 0x3f3f3f3f3f3f3f3f;
 31 
 32 int cnt;
 33 int n, m;
 34 const int maxn = 300010;
 35 int v[maxn];
 36 
 37 struct Edge
 38 {
 39     int u, nxt;
 40     int w;
 41 }e[maxn * 3];
 42 
 43 int head[maxn * 3];
 44 
 45 void add(int a, int b, int w)
 46 {
 47     e[++cnt].u = b;
 48     e[cnt].nxt = head[a];
 49     head[a] = cnt;
 50     e[cnt].w = w;
 51 }
 52 
 53 int dis[maxn * 3];
 54 bool vis[maxn * 3];
 55 queue<int>q;
 56 
 57 void spfa(int x)
 58 {
 59     mem(dis, -0x3f);
 60     mem(vis, false);
 61     dis[x] = 0;
 62     q.push(x);
 63     vis[x] = true;
 64     while (!q.empty())
 65     {
 66         int t = q.front();
 67         q.pop();
 68         vis[t] = false;
 69         for (Re int i = head[t]; i != -1; i = e[i].nxt)
 70         {
 71             int u = e[i].u;
 72             int w = e[i].w;
 73             if (dis[u] < dis[t] + w)
 74             {
 75                 dis[u] = dis[t] + w;
 76                 if (!vis[u])
 77                 {
 78                     q.push(u);
 79                     vis[u] = true;
 80                 }
 81             }
 82         }
 83     }
 84 }
 85 
 86 int main()
 87 {
 88     mem(head, -1);
 89     cin >> n >> m;
 90     mfor(i, 1, n) cin >> v[i];
 91     mfor(i, 1, m)
 92     {
 93         int a, b, c;
 94         cin >> b >> c >> a;
 95         add(b, c, 0);
 96         add(n + b, n + c, 0);
 97         add((n << 1) + b, (n << 1) + c, 0);
 98         add(b, n + c, -v[b]);
 99         add(n + b, (n << 1) + c, v[b]);
100         if (a == 2)
101         {
102             add(c, b, 0);
103             add(n + c, n + b, 0);
104             add((n << 1) + c, (n << 1) + b, 0);
105             add(c, n + b, -v[c]);
106             add(n + c, (n << 1) + b, v[c]);
107         }
108     }
109     add(n, 3 * n + 1, 0);
110     add(n * 3, n * 3 + 1, 0);
111     spfa(1);
112     cout << dis[n * 3 + 1];
113     return 0;
114 }