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1554. Minimum Time to Collect All Apples in a Tree

My accepted C++ solution to LeetCode problem 1554, Minimum Time to Collect All Apples in a Tree, running in 43ms.

  • Difficulty: Medium
  • C++
  • Runtime 43ms
  • Memory 65.5MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

C++

Accepted on LeetCode — runtime 43ms, memory 65.5MB, accepted 2025-12-27.

cpp
class Solution {
    public:
    int minTime(int n, vector<vector<int>>& edges, vector<bool>& hasApple) {
        vector<vector<int>> adj(n);
        for (auto& e : edges) {
            adj[e[0]].push_back(e[1]);
            adj[e[1]].push_back(e[0]);
        }

        return dfs(0, -1, adj, hasApple);
    }

    int dfs(int node, int parent, vector<vector<int>>& adj, vector<bool>& hasApple) {
        int totalTime = 0;
        for (int child : adj[node]) {
            if (child == parent) continue;
            int childTime = dfs(child, node, adj, hasApple);
            if (childTime > 0 || hasApple[child]) {
                totalTime += childTime + 2;
            }
        }
        return totalTime;
    }
};

Source