CodeVS1611_APIO2009_抢掠计划_C++

　　题目：http://codevs.cn/problem/1611/

　　关于题解请戳这里：http://www.cnblogs.com/hadilo/p/5892765.html

　　下面给一个可以A的代码，由于没有无限栈只能用手写栈Tarjan，上面题解里给的代码是递归栈的Tarjan，会RE

 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 #include <vector>
 #include <queue>
 #include <stack>
 #define nil 0
 #define N 500005
 using namespace std;

 int n, m, csh[N], S, P, f[N];
 int u[N << ], v[N << ], nxt[N << ], pnt[N], e;
 int dfn[N], low[N], isin[N], hcash[N], tot, indx;
 bool instack[N], vis[N];
 int Sta[N], stop;
 vector <int> g[N];
 stack <int> s;
 void add(int a, int b)
 {
     u[++e] = a; v[e] = b;
     nxt[e] = pnt[a]; pnt[a] = e;
 }
 void tarjan(int x)
 {
     s.push(x);
     dfn[x] = low[x] = ++indx;
     Sta[++stop] = x;
     instack[x] = true;
     while(!s.empty())
     {
         int t = s.top();
         for(int i = pnt[t]; i != nil; i = nxt[i])
         {
             if(dfn[v[i]] == )
             {
                 dfn[v[i]] = low[v[i]] = ++indx;
                 Sta[++stop] = v[i]; instack[v[i]] = true;
                 s.push(v[i]);
                 break;
             }
         }
         if(t == s.top())
         {
             for(int i = pnt[t]; i != nil; i = nxt[i])
             {
                 if(dfn[v[i]] > dfn[t]) low[t] = min(low[t], low[v[i]]);
                 else if(instack[v[i]]) low[t] = min(low[t], dfn[v[i]]);
             }
             if(dfn[t] == low[t])
             {
                 ++tot;
                 int j;
                 do
                 {
                     j = Sta[stop--];
                     instack[j] = false;
                     isin[j] = tot;
                     hcash[tot] += csh[j];
                 } while(j != t);
             }
             s.pop();
         }
     }
 }
 void init()
 {
     int a, b;
     scanf("%d%d", &n, &m);
     for(int i = ; i <= m; ++i)
     {
         scanf("%d%d", &a, &b);
         add(a, b);
     }
     for(int i = ; i <= n; ++i)
     {
         scanf("%d", &csh[i]);
     }
     scanf("%d%d", &S, &P);
     for(int i = ; i <= n; ++i)
     {
         if(dfn[i] == )
         {
             tarjan(i);
         }
     }
     for(int i = ; i <= n; ++i)
     {
         for(int j = pnt[i]; j != nil; j = nxt[j])
         {
             if(isin[i] != isin[v[j]])
             {
                 g[isin[i]].push_back(isin[v[j]]);
             }
         }
     }
 }
 void work()
 {
     queue <int> Q;
     memset(vis, , sizeof(vis));
     memset(f, , sizeof(f));
     f[isin[S]] = hcash[isin[S]];
     Q.push(isin[S]);
     vis[isin[S]] = true;
     while(!Q.empty())
     {
         int t = Q.front();
         Q.pop();
         vis[t] = false;
         for(int i = ; i < g[t].size(); ++i)
         {
             if(f[g[t][i]] < f[t] + hcash[g[t][i]])
             {
                 f[g[t][i]] = f[t] + hcash[g[t][i]];
                 if(!vis[g[t][i]])
                 {
                     vis[g[t][i]] = true;
                     Q.push(g[t][i]);
                 }
             }
         }
     }
     int ans = , a;
     for(int i = ; i <= P; ++i)
     {
         scanf("%d", &a);
         ans = max(ans, f[isin[a]]);
     }
     printf("%d\n", ans);
 }
 int main()
 {
     init();
     work();
     return ;
 }

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