662. 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.

/**
 * 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 {
    map<int, pair<long long,long long>> m;
    int result() {
        unsigned long long res(0);
        for(auto& e : m) {
            res = max(res, e.second.second - e.second.first + 1);
        }
        return res;
    }
public:
    int widthOfBinaryTree(TreeNode* root, int depth = 0, unsigned long long pos = 0) {
        if(!root) return 0;
        if(!m.count(depth)) {
            m[depth] = {ULLONG_MAX, 0};
        }
        m[depth].first = min(m[depth].first, pos);
        m[depth].second = max(m[depth].second, pos);
        if(root->left) widthOfBinaryTree(root->left, depth + 1, pos * 2);
        if(root->right) widthOfBinaryTree(root->right, depth + 1, pos * 2 + 1);
        return depth ? -1 : result();
    }
};