417 sequence traversal of binary tree 1 (102. sequence traversal of binary tree, 107. level traversal of binary tree II, 199. right view of binary tree, 637. layer average of binary tree)

102. Sequence traversal of binary tree

class Solution {
    
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
    
        queue<TreeNode*> que;
        if (root != nullptr) que.push(root);

        vector<vector<int>> res;

        while (!que.empty())
        {
    
            int size = que.size();
            vector<int> temp;

            for (int i = 0; i < size; i++)
            {
    
                TreeNode* node = que.front();
                que.pop();
                temp.push_back(node->val);

                if (node->left)  que.push(node->left);
                if (node->right)  que.push(node->right);
            }
            res.push_back(temp);
        }
        return res;
    }
};

107. The level traversal of binary tree II

class Solution {
    
public:
	vector<vector<int>> levelOrderBottom(TreeNode* root) {
    
		queue<TreeNode*> que;

		vector<vector<int>> res;
		if (root != nullptr)	que.push(root);

		while (!que.empty())
		{
    
			int size = que.size();
			vector<int> temp;

			for (int i = 0; i < size; i++)
			{
    
				TreeNode* node = que.front();
				que.pop();

				temp.push_back(node->val);
				if (node->left)		que.push(node->left);
				if (node->right)	que.push(node->right);
			}
			res.push_back(temp);
		}

		reverse(res.begin(), res.end());
		return res;
	}
};

199. Right side view of binary tree

class Solution {
    
public:
    vector<int> rightSideView(TreeNode* root) {
    
        queue<TreeNode*> que;
        if (root != NULL) que.push(root);
        vector<int> result;
        while (!que.empty()) {
    
            int size = que.size();
            for (int i = 0; i < size; i++) {
    
                TreeNode* node = que.front();
                que.pop();
                if (i == (size - 1)) result.push_back(node->val); //  Put the last element of each layer into result Array 
                if (node->left) que.push(node->left);
                if (node->right) que.push(node->right);
            }
        }
        return result;
    }
};

637. The layer average of a binary tree

class Solution {
    
public:
    vector<double> averageOfLevels(TreeNode* root) {
    
        queue<TreeNode*> que;
        if (root != NULL) que.push(root);
        vector<double> result;
        while (!que.empty()) {
    
            int size = que.size();
            double sum = 0; //  Count the sum of each layer 
            for (int i = 0; i < size; i++) {
    
                TreeNode* node = que.front();
                que.pop();
                sum += node->val;
                if (node->left) que.push(node->left);
                if (node->right) que.push(node->right);
            }
            result.push_back(sum / size); //  Put the mean of each layer into the result set 
        }
        return result;
    }
};