Throwing a Party

DP_indepTree.cpp

#include <bits/stdc++.h>

using namespace std;

struct Data {
    int p;
    int w;
};

typedef pair<int, int> ii;

void solve()
{
    int n, w;
    scanf("%d %d", &n, &w);

    Data inp[n];
    inp[0].p = -1;
    inp[0].w = w;
    int inDegree[n];
    memset(inDegree, 0, sizeof(inDegree));
    for (int i = 1; i < n; i++) {
        int p;
        scanf("%d %d", &p, &w);
        p--;

        inp[i].p = p;
        inp[i].w = w;

        inDegree[p]++;
    }

    queue<int> q;
    ii dp[n]; // first: pick, second: not picked
    for (int i = 0; i < n; i++) {
        dp[i].first = inp[i].w;
        dp[i].second = 0;
    }

    for (int i = 0; i < n; i++) {
        if (inDegree[i] == 0)
            q.push(i);
    }

    // self is picked = sum of child not picked
    // self is not picked = sum of max(child picked, child not picked)
    while (q.size() > 0) { // bottom up, start from the leaves
        int cur = q.front();
        q.pop();

        if (cur == -1) // root
            continue;

        int p = inp[cur].p;
        inDegree[p]--;
        if (inDegree[p] == 0)
            q.push(p);

        dp[p].first += dp[cur].second;
        dp[p].second += max(dp[cur].first, dp[cur].second);
    }

    printf("%d\n", max(dp[0].first, dp[0].second));
}

int main()
{
    int ncase;
    scanf("%d", &ncase);

    while (ncase--)
        solve();

    return 0;
}