Dp苦手( 。
参考代码:
#ifndef LOCAL #include <bits/stdc++.h> #endif constexpr auto Inf = 0X3F3F3F3F; typedef long long LL; using namespace std; namespace IO { inline LL read() { LL o = 0, f = 1; char c = getchar(); while (c < '0' || c > '9') { if (c == '-') f = -1; c = getchar(); } while (c > '/' && c < ':') { o = o * 10 + c - '0'; c = getchar(); } return o * f; } inline char recd() { char o; while ((o = getchar()) != '(' && o != ')'); return o; } } using namespace IO; const int SIZE = 1E5 + 7, Mod = 1E9 + 7; vector<int> G[SIZE]; LL w[SIZE], Dp[SIZE][2]; int vs[SIZE]; void DFS(int u) { Dp[u][1] = w[u]; for (int e = 0; e < G[u].size(); e++) { int v = G[u][e]; DFS(v); Dp[u][0] += max(Dp[v][1], Dp[v][0]); Dp[u][1] += Dp[v][0]; } } int main() { int N = read(); for (int pos = 1; pos <= N; pos++) w[pos] = read(); for (int pos = 1, u, v; pos < N; pos++) u = read(), v = read(), G[v].push_back(u), vs[u] = 1; for (int pos = 1; pos <= N; pos++) if (!vs[pos]) { DFS(pos), printf("%lld\n", max(Dp[pos][1], Dp[pos][0])); break; } }
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