Why the code is so slow? How can I improve it?

  • 0
    class Solution {
        vector<int> temp;
        vector<vector<int>> result;
        vector<vector<int>> pathSum(TreeNode* root, int sum) {
            if( !root )
                return vector<vector<int>>();
            temp.push_back( root->val );
            if( !root->left && !root->right )
                if( sum == root->val )
                    result.push_back( temp );
            pathSum( root->left, sum - root->val );
            pathSum( root->right, sum - root->val );
            return result;

  • 0

    The code is slow because pathSum returns a copy of "result", instead of a reference to it. I don't think you can improve it without changing the return type of pathSum.

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