1101. Maximum Width of Binary Tree

Code(Language:C++)

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */

class Solution {
public:
    /**
     * @param root: the root
     * @return: the maximum width of the given tree
     */
    int widthOfBinaryTree(TreeNode * root) {
        // Write your code here
        // 類似與竖排的遍历
        if(root == NULL){
            return 0; 
        }
        std::queue<pair<TreeNode*, int>> q;
        q.push(make_pair(root, 0)); 
        int maxWidth = 1; 
        while(!q.empty()){
            int sizeQ = q.size();
            int left; 
            for(int i = 0; i < sizeQ; i++){
                pair<TreeNode*, int> tmp = q.front();
                q.pop(); 
                if(i == 0){
                   left = tmp.second; 
                }
                if(i == sizeQ - 1){
                   maxWidth = max(maxWidth, tmp.second - left + 1);
                }
                if(tmp.first->left){
                    q.push(make_pair(tmp.first->left, tmp.second * 2)); 
                }
                if(tmp.first->right){
                    q.push(make_pair(tmp.first->right, tmp.second * 2 + 1)); 
                }
            }
        }
        return maxWidth;
    }
};