POJ 1155 树形dp

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#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int INF = 0x3f3f3f3f;const int maxn = 3E3 + 10;int n, m, k, w, v, dp[maxn][maxn], num[maxn];struct Edge{int v, w;Edge* Next;};Edge res[maxn * maxn], *cur, *adj[maxn];void addEdge(int u, int v, int w){cur->v = v, cur->w = w;cur->Next = adj[u];adj[u] = cur++;}void dfs(int u, int fa){for (Edge *it = adj[u]; it; it = it->Next){int v = it->v, w = it->w;if (v == fa) continue;dfs(v, u);num[u] += num[v];for (int i = num[u]; i >= 0; i--)for (int j = 0; j <= i; j++)if (dp[u][i - j] != -INF && dp[v][j] != -INF)dp[u][i] = max(dp[u][i], dp[u][i - j] + dp[v][j] - w);}}int main(int argc, char const *argv[]){while (~scanf("%d%d", &n, &m) && n + m){cur = res;memset(adj, 0, sizeof(adj));memset(num, 0, sizeof(num));memset(dp, -0x3f, sizeof(dp));for (int i = 0; i <= n; i++) dp[i][0] = 0;for (int i = 1; i <= n - m; i++){scanf("%d", &k);for (int j = 1; j <= k; j++){scanf("%d%d", &v, &w);addEdge(i, v, w);addEdge(v, i, w);}}for (int i = n - m + 1; i <= n; i++)scanf("%d", &dp[i][1]), num[i] = 1;dfs(1, -1);for (int i = m; i >= 0; i--)if (dp[1][i] >= 0) {printf("%d\n", i); break;}}return 0;}

定义dp[i][j]表示在节点i为根节点的子树下，有j个人收看节点的最大利润。
状态转移方程是：dp[i][j]=max(dp[i][j],dp[i][j-k]+dp[son of i][k]);

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