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HDU 1520 Anniversary party (树形DP)
题意:题目给出一棵树,每个节点都有其权值。如果选择了一个节点则不可以选择其父节点,问能取得的最大值。
析:一个简单的树形DP,dp[i][0] 表示结点 i不选,dp[i][1] 表示 结点 i 选,最后选最大值就好。
代码如下:
#pragma comment(linker, "/STACK:1024000000,1024000000") #include <cstdio> #include <string> #include <cstdlib> #include <cmath> #include <iostream> #include <cstring> #include <set> #include <queue> #include <algorithm> #include <vector> #include <map> #include <cctype> #include <cmath> #include <stack> //#include <tr1/unordered_map> #define freopenr freopen("in.txt", "r", stdin) #define freopenw freopen("out.txt", "w", stdout) using namespace std; //using namespace std :: tr1; typedef long long LL; typedef pair<int, int> P; const int INF = 0x3f3f3f3f; const double inf = 0x3f3f3f3f3f3f; const LL LNF = 0x3f3f3f3f3f3f; const double PI = acos(-1.0); const double eps = 1e-8; const int maxn = 6e3 + 5; const LL mod = 1e9 + 7; const int N = 1e6 + 5; const int dr[] = {-1, 0, 1, 0, 1, 1, -1, -1}; const int dc[] = {0, 1, 0, -1, 1, -1, 1, -1}; const char *Hex[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"}; inline LL gcd(LL a, LL b){ return b == 0 ? a : gcd(b, a%b); } inline int gcd(int a, int b){ return b == 0 ? a : gcd(b, a%b); } int n, m; const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; inline int Min(int a, int b){ return a < b ? a : b; } inline int Max(int a, int b){ return a > b ? a : b; } inline LL Min(LL a, LL b){ return a < b ? a : b; } inline LL Max(LL a, LL b){ return a > b ? a : b; } inline bool is_in(int r, int c){ return r >= 0 && r < n && c >= 0 && c < m; } vector<int> G[maxn]; bool in[maxn]; int dp[maxn][2]; void dfs(int u){ for(int i = 0; i < G[u].size(); ++i){ int v = G[u][i]; dfs(v); dp[u][0] += Max(dp[v][1], dp[v][0]); dp[u][1] += dp[v][0]; } return ; } int main(){ while(scanf("%d", &n) == 1){ memset(dp, 0, sizeof dp); for(int i = 1; i <= n; ++i){ scanf("%d", &dp[i][1]); G[i].clear(); } int u, v; memset(in, false, sizeof in); while(scanf("%d %d", &u, &v) == 2 && u+v){ G[v].push_back(u); in[u] = true; } int ans; for(int i = 1; i <= n; ++i) if(!in[i]){ dfs(i); ans = Max(dp[i][0], dp[i][1]); break; } printf("%d\n", ans); } return 0; }
HDU 1520 Anniversary party (树形DP)
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