POTD Solutions

GeeksforGeeks Java Solutions

Java solutions for GeeksforGeeks problems with step-by-step explanations on 230+ problems, plus approach notes and complexity analysis across the full archive.

740

Solved

230

Explained

LeetCode C#Topics Study Guide

740 problemsFull explanation available

#	Title
1	0 - 1 Knapsack Problem
2	1s Surrounded by 0s
3	2D Difference Array
4	2D Submatrix Sum Queries
5	Activity Selection
6	Add 1 to a Linked List Number
7	Add Binary Strings
8	Add Number Linked Lists
9	Adding Ones
10	Adventure in a Maze
11	Aggressive Cows
12	Alien Dictionary
13	All numbers with specific difference
14	All Subsets Xor Sum
15	All Unique Permutations of an array
16	Allocate Minimum Pages
17	Alternate positive and negative numbers
18	Alternative Sorting
19	Anagram
20	Anagram Palindrome
21	Ancestors in Binary Tree
22	AND In Range
23	Array Duplicates
24	Array to BST
25	Articulation Point - II
26	ASCII Range Sum
27	Assign Mice Holes
28	Balancing Consonants and Vowels Ratio
29	Balancing with Distinct Powers
30	Bellman-Ford
31	BFS of graph
32	Binary Searchable Count
33	Binary Strings with Equal Sum of Two Halves
34	Binary Tree to DLL
35	Bird and Max Fruit Gathering
36	Bitonic Point
37	Boolean Parenthesization
38	Bottom View of Binary Tree
39	Box Stacking
40	Brackets in Matrix Chain Multiplication
41	Bridge edge in a graph
42	BST to greater sum tree
43	BST with Dead End
44	Buildings with Sunlight
45	Burning Tree
46	Bus Conductor
47	Bus Ticket Change
48	Buy Stock with Transaction Fee
49	Candy
50	Case-specific Sorting of Strings
51	Check for BST
52	Check for Power
53	Check if a String is Subsequence of Other
54	Check if All Bits Set
55	Check if an Array is Max Heap
56	Check if frequencies can be equal
57	Check if subtree
58	Check If two Line segments Intersect
59	Check Level Anagrams in Binary Trees
60	Check Preorder of BST
61	Check Repeated Substring with K Replacements
62	Check Subset sum divisible by k
63	Chocolate Distribution Problem
64	Chocolate Pickup II
65	Chocolates Pickup
66	Choose and Swap
67	Circle of strings
68	Clone a linked list with next and random pointer
69	Clone an Undirected Graph
70	Clone List with Next and Random
71	Closest Neighbour in BST
72	Closest Three Sum
73	Coils in Matrix
74	Coin Change (Count Ways)
75	Coin Change (Minimum Coins)
76	Coin Piles
77	Common in 3 Sorted Arrays
78	Compare two fractions
79	Consecutive 1's not allowed
80	Construct a Full Binary Tree
81	Construct an array from its pair-sum array
82	Construct Binary Tree from Parent Array
83	Construct List using XOR Queries
84	Construct Tree from Inorder & Preorder
85	Construct Tree from Preorder & Postorder
86	Container With Most Water
87	Convert One String to Another with Constraints
88	Count all triplets with given sum in sorted array
89	Count Derangements
90	Count distinct elements in every window
91	Count elements less than or equal to k in a sorted rotated array
92	Count increasing Subarrays
93	Count Indices That Escape Array
94	Count Indices to Balance Even and Odd Sums
95	Count Inversions
96	Count Linked List Nodes
97	Count Matching Subsequences
98	Count Numbers Containing Specific Digits
99	Count of distinct substrings
100	Count Pairs Divisible By K
101	Count pairs Sum in matrices
102	Count Pairs Violating BST Property
103	Count Pairs whose sum is less than target
104	Count pairs with given sum
105	Count Palindromic Strings with Constraints
106	Count Prefix-Balanced Binary Strings
107	Count Reverse Pairs
108	Count set bits
109	Count Smaller elements
110	Count Sorted Digit Groupings
111	Count Spanning Trees in a Graph
112	Count Subarray with k odds
113	Count Subarrays with given XOR
114	Count Subsequences Divisible by n
115	Count Subset With Target Sum II
116	Count the Coprimes
117	Count the number of possible triangles
118	Count the paths
119	Count Tree Paths With Limited Max Edge Weight
120	Count Unique Vowel Strings
121	Count ways to N'th Stair(Order does not matter)
122	Count X in Range of a Sorted Array
123	Counting elements in two arrays
124	Course Schedule I
125	Course Schedule II
126	Coverage of all Zeros in a Binary Matrix
127	Cut Matrix
128	Cut rope to maximise product
129	Cutting Binary String
130	Decode the string
131	Delete Alternate Nodes
132	Delete node in Doubly Linked List
133	Delete Nodes with Greater on Right
134	Deletion and Reverse in Circular Linked List
135	Design MinMax Queue
136	Detect Loop in linked list
137	DFS of Graph
138	Diameter of a Binary Tree
139	Dice throw
140	Difference Check
141	Dijkstra Algorithm
142	Directed Graph Cycle
143	Distance of nearest cell having 1
144	Distribute Candies
145	Divisible by 13
146	Dominant Pairs
147	Duplicate Subtrees
148	Edit Distance
149	Elements in range [a, b]
150	Elements in the Range
151	Equal Point in Brackets
152	Equalize All Prefix Sums
153	Equalize the Towers
154	Equilibrium Point
155	Evaluation of Postfix Expression
156	Exactly one swap
157	Exit Point in a Matrix
158	Express as Consecutive Number Sum
159	Expression Add Operators
160	Expression contains redundant bracket or not
161	Extract the Number from the String
162	Facing the sun
163	Farthest Smaller Right
164	Find all possible palindromic partitions of a String
165	Find All Triplets with Zero Sum
166	Find H-Index
167	Find K Smallest Sum Pairs
168	Find Kth Rotation
169	Find length of Loop
170	Find maximum volume of a cuboid
171	Find median in a stream
172	Find Only Repetitive Element from 1 to n-1
173	Find rectangle with corners as 1
174	Find the closest pair from two arrays
175	Find the first node of loop in linked list
176	Find the longest string
177	Find the number of islands
178	Find the Sum of Last N nodes of the Linked List
179	Finding Profession
180	Fixing Two nodes of a BST
181	Flattening a Linked List
182	Flip to Maximize 1s
183	Flood fill Algorithm
184	Floyd Warshall
185	Form a palindrome
186	Form the Largest Number
187	Friends Pairing Problem
188	Frog Jump
189	Game of XOR
190	Game with String
191	Gas Station
192	Geek in a Maze
193	Generate all binary strings
194	Generate Binary Numbers
195	Generate IP Addresses
196	Generate Permutations of an array
197	Get Min from Stack
198	Get Minimum Squares
199	Gold Mine Problem
200	Graph Diameter
201	Gray Code
202	Group Balls by Sequence
203	Happiest Triplet
204	Height of Binary Tree
205	High Effort vs Low Effort
206	Histogram Max Rectangular Area
207	Huffman Encoding
208	Identical Linked Lists
209	Implement Atoi
210	Implement k Queues in a Single Array
211	Implement Pow
212	Implement Trie
213	Indexes of Subarray Sum
214	Inorder Traversal
215	Insert in Sorted Circular Linked List
216	Insert in Sorted way in a Sorted DLL
217	Insert Interval
218	Integral Points Inside Triangle
219	Interleave the First Half of the Queue with Second Half
220	Interleaved Strings
221	Intersection in Y Shaped Lists
222	Intersection of Two arrays with Duplicate Elements
223	Intersection of Two Sorted Arrays
224	Intersection Point in Y Shaped Linked Lists
225	Is Binary Tree Heap
226	Is Linked List Length Even
227	Job Sequencing Problem
228	Josephus problem
229	K closest elements
230	K Closest Points to Origin
231	K closest Values
232	k largest elements
233	K Sized Subarray Maximum
234	K Sum Paths
235	k Times Appearing Adjacent Two 1's
236	K-Pangrams
237	K-th element of two Arrays
238	K-th Largest Sum Contiguous Subarray
239	k-th Smallest in BST
240	Kadane's Algorithm
241	Koko Eating Bananas
242	Kth distance
243	Kth element in Matrix
244	Kth Largest in a Stream
245	Kth Missing Positive Number in a Sorted Array
246	Kth Smallest
247	Kth Smallest Number in Multiplication Table
248	Largest BST
249	Largest Divisible Subset
250	Largest number in K swaps
251	Largest number in one swap
252	Largest Odd Squares with Limited 1s
253	Largest Pair Sum
254	Largest Rectangle with Column Swaps
255	Largest square formed in a matrix
256	Largest subarray of 0's and 1's
257	Largest Subsquare Surrounded by X
258	Largest Sum Cycle
259	Largest Unblocked Submatrix
260	Largest with Same Parity Adjacent Swaps
261	Largest Zigzag Sequence
262	Last Coin in a Game of Alternates
263	Last Digit of a^b
264	Last Moment Before All Ants Fall Out
265	LCM Triplet
266	LCS of three strings
267	Left Rotate Matrix K times
268	Left View of Binary Tree
269	Length of Longest Cycle in a Graph
270	Level Order in spiral form
271	Level order traversal
272	Lexicographically Largest String After Deleting K Characters
273	Lexicographically smallest after removing k
274	Lexicographically Smallest Rotation
275	Linked List Group Reverse
276	Linked List Matrix
277	Linked list of strings forms a palindrome
278	Longest alternating subsequence
279	Longest Bitonic Subarray
280	Longest Bounded-Difference Subarray
281	Longest Colored Path
282	Longest Common Increasing Subsequence
283	Longest Common Prefix of Strings
284	Longest Common Subsequence
285	Longest Common Substring
286	Longest Consecutive Subsequence
287	Longest Increasing Path in Matrix
288	Longest Increasing Subsequence
289	Longest Matching in Dictionary with Removals
290	Longest Palindrome in a String
291	Longest Palindromic Subsequence
292	Longest Path in a Directed Acyclic Graph
293	Longest Periodic Proper Prefix
294	Longest Possible Route in a Matrix with Hurdles
295	Longest Prefix Suffix
296	Longest Repeating Character Replacement
297	Longest Span in two Binary Arrays
298	Longest String Chain
299	Longest Subarray Length
300	Longest subarray with Atmost two distinct integers
301	Longest Subarray with Majority Greater than K
302	Longest Subarray with Sum K
303	Longest Subsequence with Adjacent Diff as 1
304	Longest substring with distinct characters
305	Longest Substring with K Uniques
306	Longest valid Parentheses
307	Look and Say Pattern
308	Lowest Common Ancestor in a BST
309	LRU Cache
310	Majority Element
311	Majority Element II
312	Majority Vote
313	Make array elements unique
314	Make Binary Tree From Linked List
315	Make Matrix Beautiful
316	Make Strings Equal
317	Make the array beautiful
318	Marks from Ranks
319	Matrix Chain Multiplication
320	Max Absolute Diff of Two Subarrays
321	Max Adjacent Diffs Sum with 1 Replacements
322	Max After m Range Increments
323	Max Amount by Selling K Tickets
324	Max Circular Subarray Sum
325	Max DAG Edges
326	Max Digit Sum Number in 1 to n
327	Max distance between same elements
328	Max Dot Product with 0 Insertions
329	Max Gap Between Two Same
330	Max min Height
331	Max of min for every window size
332	Max Path Sum Between Two Leaves
333	Max Product Subsequence of Size K
334	Max Product Subset
335	Max Profit from Two Machines
336	Max rectangle
337	Max Score from Subarray Mins
338	Max Subarray Sum by Removing At Most One
339	Max sum in the configuration
340	Max Sum Increasing Subsequence
341	Max sum path in two arrays
342	Max Sum Subarray of Size at least K
343	Max Sum Subarray of size K
344	Max Xor Subarray of size K
345	Maximise String Score
346	Maximize Array Value After Rearrangement
347	Maximize median after doing k addition operation
348	Maximize Number of 1's
349	Maximize partitions in a String
350	Maximize The Cut Segments
351	Maximize the minimum difference between k elements
352	Maximum Area Between Bars
353	Maximum Connected group
354	Maximum Difference
355	Maximum Frequency with K Increments
356	Maximum Height Disc Stack
357	Maximum Non-Adjacent Nodes Sum
358	Maximum Non-Overlapping Odd Palindrome Sum
359	Maximum number of overlapping Intervals
360	Maximum Number of People Defeated
361	Maximum of minimum for every window size
362	Maximum Packages within Time
363	Maximum path sum
364	Maximum path sum from any node
365	Maximum People Visible in a Line
366	Maximum Product Subarray
367	Maximum product subset of an array
368	Maximum Reachable Index Difference
369	Maximum Stone Removal
370	Maximum subarray sum 2
371	Maximum Subarray Sum with One Square Allowed
372	Maximum Subset XOR
373	Maximum Sum Combination
374	Maximum sum of elements not part of LIS
375	Maximum sum of Non-adjacent nodes
376	Maximum Sum Problem
377	Maximum sum Rectangle
378	Maximum Weight Transformation of String
379	Maximum Without 3 Consecutive Set Bits
380	Maximum XOR of two numbers in an array
381	Mean of range in array
382	Median in a row-wise sorted Matrix
383	Median of BST
384	Median of two sorted arrays
385	Meeting Rooms
386	Meeting Rooms III
387	Merge K sorted linked lists
388	Merge Sort for Linked List
389	Merge two BST 's
390	Merge two sorted linked lists
391	Merge Without Extra Space
392	Middle of a Linked List
393	Min Add to Make Parentheses Valid
394	Min Chars to Add for Palindrome
395	Min Cost Climbing Stairs
396	Min Cost To Make Two Strings Identical
397	Min Edge Movements to Connect a Graph
398	Min Edge Reversals for Path
399	Min Product Subset
400	Min Steps by Knight
401	Min Swaps to Group 1s
402	Minimal Cost
403	Minimize Max Min Diff with Subarray Removal
404	Minimize the Heights I
405	Minimize the Heights II
406	Minimum Absolute Difference In BST
407	Minimum Cost for n Characters
408	Minimum Cost of ropes
409	Minimum Cost Path
410	Minimum Cost Pizza Selection
411	Minimum Cost Selection
412	Minimum cost to connect all houses in a city
413	Minimum Cost to cut a board into squares
414	Minimum Cost to Cut a Stick of length N
415	Minimum Cost to Fill Given Weight
416	Minimum Cost to Merge Stones
417	Minimum days to make M bouquets
418	Minimum Deletions
419	Minimum Deletions to Make Sorted
420	Minimum Elements Outside Subsequences
421	Minimum height roots
422	Minimum Increment or Double Operations to Convert
423	Minimum Insert and Delete to Convert
424	Minimum Jumps
425	Minimum K Consecutive Bit Flips
426	Minimum Moves to Sort Permutation
427	Minimum Multiplications to reach End
428	Minimum number of deletions and insertions
429	Minimum Number of Workers
430	Minimum Operations to Connect Hospitals
431	Minimum Operations to Reach n
432	Minimum Platforms
433	Minimum repeat to make substring
434	Minimum Squares with Full Cuts
435	Minimum Steps to Halve Sum
436	Minimum sum
437	Minimum Sum Subarray
438	Minimum Time to Finish Project
439	Minimum Toggle to Partition
440	Minimum Weight Cycle
441	Minimum Window Subsequence
442	Mirror Tree
443	Missing And Repeating
444	Missing Element in Range
445	Missing element of AP
446	Missing in Array
447	Mobile numeric keypad
448	Modify the Array
449	Mother Vertex
450	Mountain Subarray Queries
451	Move All Zeroes to End
452	Multiply two linked lists
453	Multiply two strings
454	N meetings in one room
455	N-Digit Numbers with Increasing Digits
456	N-Queen Problem
457	nCr
458	Nearest multiple of 10
459	Nearly sorted
460	Negative Weight Cycle
461	Next element with greater frequency
462	Next Greater Element
463	Next Greater Element in Circular Array
464	Next Permutation
465	Next Smallest Palindrome
466	Nine Divisors
467	Node and Ancestor Max Diff
468	Non Repeating Character
469	Non-Attacking Black and White Knights
470	Non-overlapping Intervals
471	Not a subset sum
472	Nth in Concatenated Decimal String
473	Nth Natural Number
474	Number of BST From Array
475	Number of distinct subsequences
476	Number of occurrence
477	Number of pairs
478	Number of paths in a matrix with k coins
479	Number of Rectangles in a Circle
480	Number of Turns in Binary Tree
481	Number of Ways to Arrive at Destination
482	Numbers with Given Digit Sum
483	Numbers Without d as Digit
484	Occurence of an integer in a Linked List
485	Opposite Sign Pair Reduction
486	Optimal binary search tree
487	Optimal File Merge
488	Optimal Strategy For A Game
489	Overlapping Intervals
490	Painting the Fence
491	Pair Sum in BST
492	Pair with given sum in a sorted array
493	Pairs with certain difference
494	Pairs with difference k
495	Pairs with Given GCD and LCM
496	Pairs with Less Than K Diff
497	Palindrome Linked List
498	Palindrome Pairs
499	Palindrome Sentence
500	Palindrome SubStrings
501	Palindrome with Replacement
502	Parenthesis Checker
503	Partition Equal Subset Sum
504	Partitions with Given Difference
505	Party in Town
506	Pascal Triangle
507	Path With Minimum Effort
508	Peak element
509	Perimeter of Shapes in Binary Matrix
510	Permutations of a String
511	Police and Thieves
512	Populate Inorder Successor for all nodes
513	Possible Words From Phone Digits
514	Postfix Evaluation
515	Postorder Traversal
516	Power of k in factorial of n
517	Powerful Integer
518	Predecessor and Successor
519	Prime List
520	Prime Pair with Target Sum
521	Print Anagrams Together
522	Print Bracket Number
523	Print Diagonally
524	Print leaf nodes from preorder traversal of BST
525	Product array puzzle
526	Product Pair
527	Pyramid Array with Reduce Operations
528	Pythagorean Triplet
529	Queue Reversal
530	Quick Sort on Linked List
531	Range GCD Queries
532	Range LCM Queries
533	Rat in a Maze
534	Rat in a Maze Problem - I
535	Rat Maze With Multiple Jumps
536	Rearrange the Array
537	Remaining String
538	Remove all occurences of duplicates in a linked list
539	Remove BST keys outside given range
540	Remove Duplicates
541	Remove duplicates in array
542	Remove Half Nodes
543	Remove Invalid Parentheses
544	Remove loop in Linked List
545	Remove Spaces
546	Remove the balls
547	Reorganize The Array
548	Replace O's with X's
549	Replace with XOR of Adjacent
550	Reverse a Doubly Linked List
551	Reverse a linked list
552	Reverse an Array
553	Reverse Words
554	Roll Characters of String
555	Roman Number to Integer
556	Roof Top
557	Root to leaf path sum
558	Root to Leaf Paths
559	Root to leaf paths sum
560	Rotate a Linked List
561	Rotate and delete
562	Rotate Array
563	Rotate by 90 degree
564	Rotate Deque By K
565	Rotten Oranges
566	Row with max 1s
567	Safe States
568	Search for Subarray
569	Search in a Row-Column sorted matrix
570	Search in a row-wise sorted matrix
571	Search in a sorted Matrix
572	Search in an almost Sorted Array
573	Search in fully rotated sorted 2D matrix
574	Search in Rotated Sorted Array
575	Search insert position of K in a sorted array
576	Search Pattern (KMP-Algorithm)
577	Search Pattern (Rabin-Karp Algorithm)
578	Seating Arrangement
579	Second Best Minimum Spanning Tree
580	Second Largest
581	Secret Cipher
582	Segregate 0s and 1s
583	Sequences where Adjacent Divide
584	Serialize and deserialize a binary tree
585	Set Matrix Zeroes
586	Set Matrix Zeros
587	Shop in Candy Store
588	Shortest Common Supersequence
589	Shortest Cycle
590	Shortest Path From 1 To n
591	Shortest Path in 1-2 Graph
592	Shortest path in Undirected Graph
593	Shortest Path in Weighted undirected graph
594	Shortest Path Using Atmost One Curved Edge
595	Shortest Safe Route in Grid
596	Shortest Unique Prefix for Every Word
597	Single Number
598	Size of Binary Tree
599	Smallest distinct window
600	Smallest Divisor
601	Smallest Non-Zero Number
602	Smallest number
603	Smallest Positive Missing
604	Smallest Positive Missing Number
605	Smallest range in K lists
606	Smallest window containing 0, 1 and 2
607	Smallest window containing all characters
608	Smallest window in a string containing all the characters of another string
609	Snake and Ladder Problem
610	Solve the Sudoku
611	Sort 0s, 1s and 2s
612	Sort a k sorted doubly linked list
613	Sort a linked list of 0s, 1s and 2s
614	Sort by Absolute Difference
615	Sort in specific order
616	Sort the given array after applying the given equation
617	Sort Two Parts Sorted
618	Sorted and Rotated Minimum
619	Sorted subsequence of size 3
620	Sorting Elements of an Array by Frequency
621	Spirally traversing a matrix
622	Split an array into two equal Sum subarrays
623	Split array in three equal sum subarrays
624	Split Array into Minimum Subsets
625	Split Array Largest Sum
626	Split Array Subsequences
627	Split Linked List Alternatingly
628	Split the Array
629	Square root of a number
630	Stable Marriage Problem
631	Stickler Thief
632	Stickler Thief II
633	Stock Buy and Sell – Max 2 Transactions Allowed
634	Stock Buy and Sell – Max K Transactions Allowed
635	Stock Buy and Sell – Max one Transaction Allowed
636	Stock Buy and Sell – Multiple Transaction Allowed
637	Stock Buy and Sell with Cooldown
638	Stock span problem
639	Stream First Non-repeating
640	String stack
641	Strings Rotations of Each Other
642	Sub-arrays with equal number of occurences
643	Subarray Frequency Count Queries
644	Subarray range with given sum
645	Subarrays With At Most K Distinct Integers
646	Subarrays with First Element Minimum
647	Subarrays with Sum in Range
648	Subarrays with sum K
649	Subset Sum on Generated Sequence
650	Subset Sum Problem
651	Subset XOR
652	Subsets with MEX in Range
653	Subsets with Products of Distinct Primes
654	Substring with Max Zero-One Diff
655	Substrings of length k with k-1 distinct elements
656	Substrings with K Distinct
657	Substrings with more 1's than 0's
658	Substrings with same first and last characters
659	Successful Binary Searches Irrespective of Pivot
660	Sum of all substrings of a number
661	Sum of Beauty of All Substrings
662	Sum of Mode
663	Sum of Nodes in BST Range
664	Sum of nodes on the longest path
665	Sum of Pairwise ANDs
666	Sum of subarray minimum
667	Sum of subarray minimums
668	Sum of subarray ranges
669	Sum of Subarrays
670	Sum of XOR of all pairs
671	Sum Pair closest to target
672	Sum Tree
673	Sum-string
674	Summed Matrix
675	Swap and Maximize
676	Swap diagonals
677	Swap Kth nodes from ends
678	Symmetric Tree
679	Target Sum
680	The Celebrity Problem
681	The Knight's tour problem
682	The Painter's Partition Problem-II
683	The Palindrome Pattern
684	Toeplitz matrix
685	Top K Frequent in Array
686	Top View of Binary Tree
687	Topological sort
688	Total count
689	Total Decoding Messages
690	Towers Reaching Both Stations
691	Trace Path
692	Trail of ones
693	Transform String
694	Transform to Sum Tree
695	Transpose of Matrix
696	Trapping Rain Water
697	Travelling Salesman Problem
698	Tree Boundary Traversal
699	Triplet Family
700	Triplets with Sum in Range
701	Two Equal Sum Subarrays
702	Two Smallests in Every Subarray
703	Two Sum - Pair with Given Sum
704	Two Swaps
705	Two water Jug problem
706	Tywin's War Strategy
707	Undirected Graph Cycle
708	Union of Arrays with Duplicates
709	Union of Two Sorted Arrays with Distinct Elements
710	Unique K-Number Sum
711	Unique Number I
712	Unique Number II
713	Unique Number III
714	Unique Paths in a Grid
715	Unoccupied Computers
716	URLify a given string
717	Validate an IP Address
718	Values with Equal Array Remainders
719	Vertical Sum
720	Vertical Tree Traversal
721	Vertical Width of a Binary Tree
722	Visit Leaves with Budget
723	Walls Coloring II
724	Ways to Express as Sum of Consecutives
725	Ways to Increase LCS by One
726	Ways to Reach Origin
727	Ways to Reach the n'th Stair
728	Ways To Tile A Floor
729	Ways to Tile the Floor
730	Weighted Job Scheduling
731	Wifi Range
732	Wildcard Pattern Matching
733	Word Break
734	Word in Grid - All Occurrences
735	Word Search
736	XOR Linked List
737	XOR of All Subarray XORs
738	XOR Pairs less than K
739	Your Social Network
740	ZigZag Tree Traversal