LeetCode: Sum of Distances in Tree

class Solution {
public:

    vector <int> g[300010];
    int node[300010], dpchild[300010];
    bool vs[300010];

    void dfs(int u, int p){
        if(vs[u]) return;
        vs[u] = true;
        node[u] = 1;
        dpchild[u] = 0;
        for(auto v: g[u]){
            if(p != v){
                dfs(v, u);
                node[u] += node[v];
                dpchild[u] += dpchild[v] + node[v];
            }
        }
    }

    void DP(int u, int p, vector <int> &dp, int n){
        if(vs[u]) return;
        vs[u] = true;
        int dppar = (dp[p] - dpchild[u] - node[u]) + (n - node[u]); /// dpchild + node
        dp[u] = dpchild[u] + (u == 0 ? 0 : dppar);
        for(auto v: g[u]){
            if(v != p) DP(v, u, dp, n);
        }
    }

    vector<int> sumOfDistancesInTree(int n, vector<vector<int>>& edges) {
        int sz = edges.size();
        for(int i=0;i<=sz-1;i++){
            int u = edges[i][0];
            int v = edges[i][1];
            g[u].push_back(v);
            g[v].push_back(u);
        }

        for(int u=0;u<=n-1;u++) vs[u] = false;
        dfs(0, 0);

        vector <int> dp(n, 0);
        for(int u=0;u<=n-1;u++) vs[u] = false;
        DP(0, 0, dp, n);

        return dp;
    }
};