import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/**

 You need to find the largest value in each row of a binary tree.

 Example:
 Input:

    1
   / \
  3   2
 / \   \
5   3   9

 Output: [1, 3, 9]

 */

public class Find_Largest_Value_in_Each_Tree_Row {

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
    class Solution {
        public List<Integer> largestValues(TreeNode root) {

            List<Integer> result = new ArrayList<>();

            // bfs
            if (root == null) {
                return result;
            }

            Queue<TreeNode> q = new LinkedList<>();
            q.offer(root);
            int currentLevelCount = 1;
            int nextLevelCount = 0;

            int currentLevelMax = root.val;

            while (!q.isEmpty()) {
                TreeNode current = q.poll();
                currentLevelCount--;

                // check leftmost
                currentLevelMax = Math.max(currentLevelMax, current.val);

                if (current.left != null) {
                    q.offer(current.left);
                    nextLevelCount++;
                }
                if (current.right != null) {
                    q.offer(current.right);
                    nextLevelCount++;
                }

                if (currentLevelCount == 0) {
                    currentLevelCount = nextLevelCount;
                    nextLevelCount = 0;

                    result.add(currentLevelMax);

                    // reset
                    currentLevelMax = Integer.MIN_VALUE;
                }
            }

            return result;
        }
    }
}

// OJ: https://leetcode.com/problems/find-largest-value-in-each-tree-row/
// Time: O(N)
// Space: O(N)
class Solution {
public:
    vector<int> largestValues(TreeNode* root) {
        if (!root) return {};
        vector<int> ans;
        queue<TreeNode*> q{ {root} };
        while (q.size()) {
            int cnt = q.size(), maxVal = INT_MIN;
            while (cnt--) {
                auto n = q.front();
                q.pop();
                maxVal = max(maxVal, n->val);
                if (n->left) q.push(n->left);
                if (n->right) q.push(n->right);
            }
            ans.push_back(maxVal);
        }
        return ans;
    }
};

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def largestValues(self, root: Optional[TreeNode]) -> List[int]:
        if root is None:
            return []
        q = deque([root])
        ans = []
        while q:
            t = -inf
            for _ in range(len(q)):
                node = q.popleft()
                t = max(t, node.val)
                if node.left:
                    q.append(node.left)
                if node.right:
                    q.append(node.right)
            ans.append(t)
        return ans

############

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
  def largestValues(self, root):
    """
    :type root: TreeNode
    :rtype: List[int]
    """
    ans = []
    d = {}

    def dfs(root, h, d):
      if root:
        dfs(root.left, h + 1, d)
        dfs(root.right, h + 1, d)
        d[h] = max(d.get(h, float("-inf")), root.val)

    dfs(root, 0, d)
    level = 0
    while level in d:
      ans += d[level],
      level += 1
    return ans

515 - Find Largest Value in Each Tree Row

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