2022-02-27 Daily-Challenge

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In: DailyChallenge
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Today I have done leetcode's February LeetCoding Challenge with cpp.

February LeetCoding Challenge 27

Description

Maximum Width of Binary Tree

Given the root of a binary tree, return the maximum width of the given tree.

The maximum width of a tree is the maximum width among all levels.

The width of one level is defined as the length between the end-nodes (the leftmost and rightmost non-null nodes), where the null nodes between the end-nodes are also counted into the length calculation.

It is guaranteed that the answer will in the range of 32-bit signed integer.

Example 1:

img

Input: root = [1,3,2,5,3,null,9]
Output: 4
Explanation: The maximum width existing in the third level with the length 4 (5,3,null,9).

Example 2:

img

Input: root = [1,3,null,5,3]
Output: 2
Explanation: The maximum width existing in the third level with the length 2 (5,3).

Example 3:

img

Input: root = [1,3,2,5]
Output: 2
Explanation: The maximum width existing in the second level with the length 2 (3,2).

Constraints:

  • The number of nodes in the tree is in the range [1, 3000].
  • -100 <= Node.val <= 100

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  int widthOfBinaryTree(TreeNode* root) {
    if(!root) return 0;
    long long answer = 0;
    queue<pair<long long, TreeNode*>> q;
    q.push({0, root});
    while(q.size()) {
      int sz = q.size();
      long long mmin = INT_MAX;
      long long mmax = INT_MIN;
      for(int _ = 0; _ < sz; ++_) {
        auto [index, cur] = q.front();
        mmin = min(index, mmin);
        mmax = max(index, mmax);
        q.pop();
        if(cur->left) q.push({index * 2 - mmin, cur->left});
        if(cur->right) q.push({index * 2 + 1 - mmin, cur->right});
      }
      answer = max(answer, mmax - mmin + 1);
    }
    return answer;
  }
};

// Accepted
// 113/113 cases passed (18 ms)
// Your runtime beats 28.12 % of cpp submissions
// Your memory usage beats 21.15 % of cpp submissions (17.4 MB)
Algorithm