「POJ 2342」没有上司的晚会

#include <bits/stdc++.h>
using namespace std;
char ch;
bool signum;
inline void readInt(int& l) {
    l = 0;
    do
        ch = cin.get();
    while ((ch < '0' || ch > '9') && ch != '-' && ch != '0');
    if (ch == '-') signum = true, ch = cin.get();
    while (ch >= '0' && ch <= '9')
        l = (l << 1) + (l << 3) + ch - '0', ch = cin.get();
    if (signum) l = -l, ch = cin.get();
}
int father[6005], vis[6005], dp[6005][2], t;
void dfs(int node) {
    vis[node] = 1;
    for (register int i = 1; i <= t; i++) {
        if (!vis[i] && father[i] == node) {
            dfs(i);
            dp[node][1] += dp[i][0];
            dp[node][0] += max(dp[i][0], dp[i][1]);
        }
    }
}
int main() {
    int l, k;
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    readInt(t);
    for (register int i = 1; i <= t; i++) readInt(dp[i][1]);
    int root = 0;
    while (readInt(l), readInt(k), l + k > 0) {
        father[l] = k;
        root = k;
    }
    memset(vis, 0, sizeof(vis));
    dfs(root);
    cout << max(dp[root][1], dp[root][0]) << endl;
    return 0;
}