Sum of Root to Leaf Binary Numbers Problem & Solution

C++ Solution

``````#pragma GCC optimize("Ofast")
#pragma GCC optimization("max-inline-insns-recursive-auto")
#pragma GCC target("avx,avx2,fma")

static const int _=[](){ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();

/**
* Definition for a binary tree node.
* struct TreeNode {
*   int val;
*   TreeNode *left;
*   TreeNode *right;
*   TreeNode() : val(0), left(nullptr), right(nullptr) {}
*   TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
*   TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
int sumRootToLeaf(TreeNode* root) {
vector<int> bits;

return sumRootToLeaf(root, bits);
}

private:
int sumRootToLeaf(TreeNode* root, vector<int>& bits) {
if (root == nullptr) {
return 0;
}

if (root->left == nullptr && root->right == nullptr) {
bits.push_back(root->val);

int base10 = 0;
for (int i = bits.size() - 1, j = 1; i >= 0; --i, j *= 2) {
base10 += bits[i] * j;
}

bits.pop_back();

return base10;
}

bits.push_back(root->val);
int sum = sumRootToLeaf(root->left, bits) +
sumRootToLeaf(root->right, bits);
bits.pop_back();

return sum;
}
};
``````

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