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软件构成了一些树和一些环, 对于环我们要不不选, 要么选整个环. 跑tarjan缩点后, 新建个root, 往每个入度为0的点(强连通分量) 连边, 然后跑树dp( 01背包 )
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#include<cstdio>
#include<cstring>
#include<stack>
#include<algorithm>
#include<vector>
#include<iostream>
#define rep(i, n) for(int i = 0; i < n; i++)
#define clr(x, c) memset(x, c, sizeof(x))
#define Rep(i, n) for(int i = 1; i <= n; ++i)
using namespace std;
const int maxn = 109, maxm = 509;
vector<int> G[maxn];
stack<int> S;
int dfn[maxn], low[maxn], scc[maxn], dfs_clock = 0, N = 0, n, m;
int W[maxn], V[maxn], w_t[maxn], v_t[maxn], d[maxn][maxm];
bool F[maxn];
void tarjan(int x) {
dfn[x] = low[x] = ++dfs_clock;
S.push(x);
for(vector<int>::iterator it = G[x].begin(); it != G[x].end(); it++)
if(!dfn[*it]) {
tarjan(*it);
low[x] = min(low[x], low[*it]);
} else if(!scc[*it])
low[x] = min(low[x], dfn[*it]);
if(low[x] == dfn[x]) {
N++;
int t;
do {
t = S.top(); S.pop();
scc[t] = N;
w_t[N] += W[t];
v_t[N] += V[t];
} while(t != x);
}
}
void TARJAN() {
clr(w_t, 0), clr(v_t, 0);
clr(scc, 0), clr(dfn, 0);
Rep(i, n) if(!dfn[i]) tarjan(i);
}
struct edge {
int to;
edge* next;
} E[maxn << 2], *pt = E, *head[maxn];
inline void add_edge(int u, int v) {
F[pt->to = v] = true;
pt->next = head[u];
head[u] = pt++;
}
void build() {
clr(F, 0), clr(head, 0);
Rep(i, n)
for(vector<int>::iterator it = G[i].begin(); it != G[i].end(); it++)
if(scc[*it] != scc[i]) add_edge(scc[i], scc[*it]);
Rep(i, N) if(!F[i])
add_edge(0, i);
}
void dp(int x) {
for(int i = v_t[x]; i <= m; i++) d[x][i] = w_t[x];
for(edge* e = head[x]; e; e = e->next) {
dp(e->to);
for(int h = m; h >= v_t[x]; h--)
for(int t = 0; t <= h - v_t[x]; t++)
d[x][h] = max(d[x][h], d[x][h - t] + d[e->to][t]);
}
}
int main() {
// freopen("test.in", "r", stdin);
cin >> n >> m;
Rep(i, n) scanf("%d", V + i);
Rep(i, n) scanf("%d", W + i);
Rep(i, n) {
int v;
scanf("%d", &v);
if(v) G[v].push_back(i);
}
TARJAN();
build();
clr(d, 0), dp(0);
cout << *max_element(d[0], d[0] + m + 1) << "\n";
return 0;
}
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BZOJ 2427: [HAOI2010]软件安装( dp )
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原文地址：http://www.cnblogs.com/JSZX11556/p/4661327.html
