uestc 方老师抢银行

参考的大牛的思路和代码

思路： 每次经过一个强连通分量时，都可以走完该分量从而使抢得的钱最多，可以把每个强连通分量缩点，用总的钱数代表该点的值。然后重新遍历新图，遇到网吧可以更新一下结果。

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstdlib>
  4 #include<cstring>
  5 #include<string>
  6 #include<queue>
  7 #include<algorithm>
  8 #include<map>
  9 #include<iomanip>
 10 #include<climits>
 11 #include<string.h>
 12 #include<cmath>
 13 #include<stdlib.h>
 14 #include<vector>
 15 #include<stack>
 16 #include<set>
 17 using namespace std;
 18 #define INF 1000000007
 19 #define MAXN 300010
 20 #define Mod 1000007
 21 #define N 100007
 22 #define NN 30
 23 #define sigma_size 3
 24 const int maxn = 6e5 + 10;
 25 using namespace std;
 26 typedef long long LL;
 27 const double pi = acos(-1);
 28
 29 vector<int> G[MAXN], G2[MAXN];
 30 int dfn[N], lowlink[N], instk[N], bel[N], coin[N], iswb[N], wb[N], coin2[N];
 31 int tot, tot2, n, m, dfs_clock, scc_cnt, p, k, res;
 32 int u, v;
 33 stack<int> S;
 34
 35 void Tarjan(int u)
 36 {
 37     dfn[u] = lowlink[u] = ++dfs_clock;
 38     S.push(u);
 39     instk[u] = 1;
 40     for (int i = 0; i < G[u].size(); ++i) {
 41         int v = G[u][i];
 42         if (!dfn[v]) {
 43             Tarjan(v);
 44             lowlink[u] = min(lowlink[u], lowlink[v]);
 45         }
 46         else if (instk[v]) {
 47             lowlink[u] = min(lowlink[u], dfn[v]);
 48         }
 49     }
 50     if (lowlink[u] == dfn[u]) {
 51         scc_cnt++;
 52         int v;
 53         do {
 54             v = S.top();
 55             S.pop();
 56             if (iswb[v]) wb[scc_cnt] = 1;
 57             instk[v] = 0;
 58             coin2[scc_cnt] += coin[v];
 59             bel[v] = scc_cnt;
 60             if (v == p) p = scc_cnt;
 61         } while (v != u);
 62     }
 63 }
 64
 65 void find_scc()
 66 {
 67     for (int i = 1; i <= n; ++i)
 68         if (!dfn[i]) Tarjan(i);
 69 }
 70
 71 void dfs(int u, int sum)
 72 {
 73     sum += coin2[u];
 74     if (wb[u]) res = max(res, sum);
 75     for (int i = 0; i < G2[u].size(); ++i)
 76         dfs(G2[u][i], sum);
 77 }
 78
 79 void init()
 80 {
 81     for (int i = 0; i <= n; ++i) {
 82         G[i].clear();
 83         G2[i].clear();
 84     }
 85     while (!S.empty()) S.pop();
 86     dfs_clock = scc_cnt = 0;
 87     memset(instk, 0, sizeof(instk));
 88     memset(dfn, 0, sizeof(dfn));
 89     memset(iswb, 0, sizeof(iswb));
 90     memset(wb, 0, sizeof(wb));
 91     memset(bel, -1, sizeof(bel));
 92     memset(coin2, 0, sizeof(coin2));
 93     memset(lowlink, 0, sizeof(lowlink));
 94 }
 95
 96 void read()
 97 {
 98     for (int i = 0; i < m; ++i) {
 99         scanf("%d%d", &u, &v);
100         G[u].push_back(v);
101     }
102     for (int i = 1; i <= n; ++i)
103         scanf("%d", &coin[i]);
104     scanf("%d%d", &p, &k);
105     for (int i = 0; i < k; ++i) {
106         scanf("%d", &v);
107         iswb[v] = 1;
108     }
109 }
110
111 void rebuild()
112 {
113     for (int i = 1; i <= n; ++i) {
114         for (int j = 0; j < G[i].size(); ++j) {
115             u = bel[i];
116             v = bel[G[i][j]];
117             if (u != v)
118                 G2[u].push_back(v);
119         }
120     }
121     res = -1;
122     dfs(p, 0);
123     cout << res << endl;
124 }
125
126 void process()
127 {
128     init();
129     read();
130     find_scc();
131     rebuild();
132 }
133
134 int main()
135 {
136     while (cin >> n >> m)
137         process();
138     //system("pause");
139     return 0;
140 }