2022-01-11 Daily-Challenge

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In: DailyChallenge

Today I have done leetcode's January LeetCoding Challenge with cpp.

January LeetCoding Challenge 11

Description

Sum of Root To Leaf Binary Numbers

You are given the root of a binary tree where each node has a value 0 or 1. Each root-to-leaf path represents a binary number starting with the most significant bit.

  • For example, if the path is 0 -> 1 -> 1 -> 0 -> 1, then this could represent 01101 in binary, which is 13.

For all leaves in the tree, consider the numbers represented by the path from the root to that leaf. Return the sum of these numbers.

The test cases are generated so that the answer fits in a 32-bits integer.

Example 1:

img

Input: root = [1,0,1,0,1,0,1]
Output: 22
Explanation: (100) + (101) + (110) + (111) = 4 + 5 + 6 + 7 = 22

Example 2:

Input: root = [0]
Output: 0

Constraints:

  • The number of nodes in the tree is in the range [1, 1000].
  • Node.val is 0 or 1.

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  int sumRootToLeaf(TreeNode* root, int cur = 0) {
    if(!root) return 0;
    cur = ((cur << 1) | root->val);
    if(!root->left && !root->right) return cur;
    return sumRootToLeaf(root->left, cur) + sumRootToLeaf(root->right, cur);
  }
};

// Accepted
// 63/63 cases passed (4 ms)
// Your runtime beats 87.29 % of cpp submissions
// Your memory usage beats 29.55 % of cpp submissions (16.8 MB)
Algorithm