199. Binary Tree Right Side View

Dhanaraj S
1 min readApr 12, 2022

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Check out the problem description here.

Solution

Approach 1

Iterative using level order traversal.

You can use level order traversal, with traversing from

a)left to right -here the last node in each level is what contribute to the right view

b)right to left -here the f irst node in each level is what contribute to right view

In the code below, we follow left to right level- order traversal.

class Solution:
def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
res=[]
q=[]
if root:
q.append([root,0])
while(q):
size = len(q)
for i in range(size):
front = q.pop(0)
x=front[1]
if front[0].left:
q.append([front[0].left,x-1])
if front[0].right:
q.append([front[0].right,x+1])
if(i==size-1):
res.append(front[0].val)
return res

Time:O(N)

Space:O(N)

Approach 2:

Recursive Solution

Traverse the tree in root,right, left fashion.Since rightmost node in each level is the right view for that particular level

class Solution:
def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
res=[]
self.rec(root,0,res)
return res

def rec(self,root,level,res):
if not root:
return
if len(res)==level:
res.append(root.val)
self.rec(root.right,level+1,res)
self.rec(root.left,level+1,res)

Time:O(N)

Space:O(h)

h->height of tree (stack space)

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Dhanaraj S

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