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Sum of Left Leaves
Bookmark
Recursive DFS
Iterative BFS
Input
Example 1 (sum=24)
Example 2 (sum=4)
Right Leaves Don't Count (sum=8)
Single Node (sum=0)
Custom
tree
=
[3, 9, 20, null, null, 15, 7]
3
9
20
15
7
sum = 0
leaves
at each node: is its
left child
a leaf?
3
9
20
15
7
sum = 0
leaves
at each node: is its
left child
a leaf?
3
9
20
15
7
sum = 0
leaves
is left child
9
a leaf?
3
9
20
15
7
sum = 9
leaves
9
recurse into the right subtree of
3
3
9
20
15
7
sum = 9
leaves
9
is left child
15
a leaf?
3
9
20
15
7
sum = 24
leaves
9
15
recurse into the right subtree of
20
3
9
20
15
7
sum = 24
leaves
9
15
call on
7
(right child)
: sum = 0
3
9
20
15
7
sum = 24
leaves
9
15
7
has no right child: +0
3
9
20
15
7
sum = 24
leaves
9
15
back at
20
: subtree returned 0
3
9
20
15
7
sum = 24
leaves
9
15
back at
3
: subtree returned 15
3
9
20
15
7
sum = 24
leaves
9
15
return 24
algo
master
.
io
Step:
Start: at each node, check whether its left child is a leaf
0 / 17
Input
Example 1 (sum=24)
Example 2 (sum=4)
Right Leaves Don't Count (sum=8)
Single Node (sum=0)
Custom
tree
=
[3, 9, 20, null, null, 15, 7]
0 / 17
algo
master
.
io
Step:
Start: at each node, check whether its left child is a leaf
