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Problem solution · C++

Create Components With Same Value

Create Components With Same Value: a C++ solution using depth-first search. Learn the idea, check the complexity, and read the full code, with credit to walkccc LeetCode Solutions.

Technique
Depth-first search
Source
walkccc LeetCode Solutions
Length
47 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Depth-first search

For Create Components With Same Value, the implementation follows one branch at a time, making it suitable for components, trees, backtracking, or dependency exploration.

  1. Define the state carried into one recursive or stack frame.
  2. Mark or choose the current state before exploring children.
  3. Combine child results or undo the choice when the branch finishes.

Code notes

  • 47 lines of C++ from the credited upstream file 2440.cpp.
  • The implementation visibly relies on sequence storage.
  • 3 loop blocks detected, together with recursive traversal.

Complexity

Count unique states for graph traversal; for backtracking, count the branching factor and maximum depth.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from walkccc LeetCode Solutions by P.-Y. Chen (walkccc) and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeCreate Components With Same Value · C++C++
Use this to learn the idea, then write your own version.
class Solution { public:  int componentValue(vector<int>& nums, vector<vector<int>>& edges) {    const int n = nums.size();    const int sum = accumulate(nums.begin(), nums.end(), 0);    vector<vector<int>> tree(n);     for (const vector<int>& edge : edges) {      const int u = edge[0];      const int v = edge[1];      tree[u].push_back(v);      tree[v].push_back(u);    }     for (int i = n; i > 1; --i)      // Split the tree into i parts, i.e. delete (i - 1) edges.      if (sum % i == 0 && dfs(nums, tree, 0, sum / i, vector<bool>(n)) == 0)        return i - 1;     return 0;  }  private:  static constexpr int kMax = 1'000'000'000;   // Returns the sum of the subtree rooted at u substracting the sum of the  // deleted subtrees.  int dfs(const vector<int>& nums, const vector<vector<int>>& tree, int u,          int target, vector<bool>&& seen) {    int sum = nums[u];    seen[u] = true;     for (const int v : tree[u]) {      if (seen[v])        continue;      sum += dfs(nums, tree, v, target, std::move(seen));      if (sum > target)        return kMax;    }     // Delete the tree that has sum == target.    if (sum == target)      return 0;    return sum;  }};

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