思路:dp[i][j]表示以i为根结点有j个连通节点的最小和, 当进行状态转移时需要利用01背包,节点u下面有多个子节点,每个子节点可以最多可以贡献cnt[v]个节点,cnt[v]表示以v为根结点的树的节点总数。
AC代码
#include <cstdio> #include <cmath> #include <cctype> #include <algorithm> #include <cstring> #include <utility> #include <string> #include <iostream> #include <map> #include <set> #include <vector> #include <queue> #include <stack> using namespace std; #pragma comment(linker, "/STACK:1024000000,1024000000") #define eps 1e-10 #define inf 0x3f3f3f3f #define PI pair<int, int> const int maxn = 2e3 + 5; int dp[maxn][maxn], w[maxn], cnt[maxn], p[maxn], ans[maxn]; int n; vector<int>G[maxn]; //dp[i][j]表示以i为根结点有j个连通节点的最小和 int dfs(int u, int pre) { int sum = 0; for(int i = 0; i < G[u].size(); ++i) { int v = G[u][i]; if(v == pre) continue; cnt[v] += dfs(v, u); sum += cnt[v]; } //p[i]表示凑足i个节点的最小和,利用了滚动数组 p[0] = 0; for(int i = 1; i <= sum; ++i) p[i] = inf; for(int i = 0; i < G[u].size(); ++i) { int v = G[u][i]; if(v == pre) continue; for(int j = sum; j >= 1; --j) { for(int k = 1; k <= cnt[v]; ++k) { if(j >= k) p[j] = min(p[j], p[j-k] + dp[v][k]); } } } for(int i = 0; i <= sum; ++i) { dp[u][i+1] = p[i] + w[u]; ans[i+1] = min(ans[i+1], dp[u][i+1]); } return sum+1; } int main() { while(scanf("%d", &n) == 1) { for(int i = 1; i <= n; ++i) { scanf("%d", &w[i]); G[i].clear(); ans[i] = inf; } int u, v; for(int i = 0; i < n-1; ++i) { scanf("%d%d", &u, &v); G[u].push_back(v); G[v].push_back(u); } dfs(1, -1); for(int i = 1; i <= n; ++i) { if(i == n) printf("%d\n", ans[i]); else printf("%d ", ans[i]); } } return 0; }
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