Skip to main content

Binary Tree Level Order Traversal - Leetcode 102 - BFS - Python

Binary Tree Level Order Traversal


Given the root of a binary tree, return the level order traversal of its nodes' values. (i.e., from left to right, level by level).



class Solution:

    def levelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:

        ans = []

        q = collections.deque()

        q.append(root)

        

        while q :

            l = len(q)

            lvl = []

            for i in range(l):

                node = q.popleft()

                if node:

                    lvl.append(node.val)

                    q.append(node.left)

                    q.append(node.right)

            if lvl:

                ans.append(lvl)

        return ans

        

Explaination :








 

Labels

Labels:

Comments

Post a Comment

Popular posts from this blog

Leetcode 371. Sum of Two Integers. C++ / Java

371 .  Sum of Two Integers   Given two integers  a  and  b , return  the sum of the two integers without using the operators   +   and   - .   Example 1: Input: a = 1, b = 2 Output: 3 Example 2: Input: a = 2, b = 3 Output: 5   Constraints: -1000 <= a, b <= 1000 Solution :  C++ : class Solution { public: int getSum(int a, int b) { if (b==0) return a; int sum = a ^ b; int cr = (unsigned int) (a & b) << 1; return getSum(sum, cr); } }; Java :  class Solution { public int getSum(int a, int b) { while(b != 0){ int tmp = (a & b) << 1; a = a ^ b; b = tmp; } return a; } } Explaination :
Post a Comment
Read more

Container with Most Water - Leetcode 11 - Python

  You are given an integer array   height   of length   n . There are   n   vertical lines drawn such that the two endpoints of the   i th   line are   (i, 0)   and   (i, height[i]) . Find two lines that together with the x-axis form a container, such that the container contains the most water. Return  the maximum amount of water a container can store . Notice  that you may not slant the container.   Input: height = [1,8,6,2,5,4,8,3,7] Output: 49 Explanation: The above vertical lines are represented by array [1,8,6,2,5,4,8,3,7]. In this case, the max area of water (blue section) the container can contain is 49. class Solution:     def maxArea(self, height: List[int]) -> int:         # ans = 0         # for l in range(len(height)):         #     for r in range(l+1, len(height)):         #      ...
Post a Comment
Read more

Leetcode 424. Longest Repeating Character Replacement. Python (Sliding Window)

  424 .  Longest Repeating Character Replacement You are given a string  s  and an integer  k . You can choose any character of the string and change it to any other uppercase English character. You can perform this operation at most  k  times. Return  the length of the longest substring containing the same letter you can get after performing the above operations .   Example 1: Input: s = "ABAB", k = 2 Output: 4 Explanation: Replace the two 'A's with two 'B's or vice versa. Example 2: Input: s = "AABABBA", k = 1 Output: 4 Explanation: Replace the one 'A' in the middle with 'B' and form "AABBBBA". The substring "BBBB" has the longest repeating letters, which is 4.   Constraints: 1 <= s.length <= 10 5 s  consists of only uppercase English letters. 0 <= k <= s.length Solution :  class Solution: def characterReplacement(self, s: str, k: int) -> int: hm = {} ans = 0 ...
Post a Comment
Read more