Trie LeetCode Problems: 49 Python Solutions

1 pattern

How Trie problems are solved

A tag names the subject, not the method. These pattern hubs cover the techniques that actually solve Trie problems — each one explains the approach, gives a Python template and states its complexity.

TrieStore a set of words by their shared prefixes so lookups cost the length of the word.

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python

Please analyze this context and help me answer the question or solve the problem.

Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

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python

Please analyze this context and help me answer the question or solve the problem.

Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

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QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

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python

Please analyze this context and help me answer the question or solve the problem.

Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

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Trie problems by difficulty

Problems with a complete Python solution are listed first, then by ascending problem number.

Easy (3)

Easy problems
No.	Problem	Topics
0014	Longest Common Prefix	Trie, Array, String
2932	Maximum Strong Pair XOR I	Bit Manipulation, Trie, Array +2
1065	Index Pairs of a StringPremium	Trie, Array, String +1

Medium (24)

Medium problems
No.	Problem	Topics
0139	Word Break	Trie, Memoization, Array +3
0208	Implement Trie (Prefix Tree)	Design, Trie, Hash Table +1
0211	Design Add and Search Words Data Structure	Depth-First Search, Design, Trie +1
0386	Lexicographical Numbers	Depth-First Search, Trie
0421	Maximum XOR of Two Numbers in an Array	Bit Manipulation, Trie, Array +1
0648	Replace Words	Trie, Array, Hash Table +1
0676	Implement Magic Dictionary	Depth-First Search, Design, Trie +2
0677	Map Sum Pairs	Design, Trie, Hash Table +1
0692	Top K Frequent Words	Trie, Array, Hash Table +5
0720	Longest Word in Dictionary	Trie, Array, Hash Table +2
0792	Number of Matching Subsequences	Trie, Array, Hash Table +4
0820	Short Encoding of Words	Trie, Array, Hash Table +1
1023	Camelcase Matching	Trie, Array, Two Pointers +2
1233	Remove Sub-Folders from the Filesystem	Depth-First Search, Trie, Array +1
1268	Search Suggestions System	Trie, Array, String +3
2261	K Divisible Elements Subarrays	Trie, Array, Hash Table +3
2452	Words Within Two Edits of Dictionary	Trie, Array, String
2707	Extra Characters in a String	Trie, Array, Hash Table +2
0616	Add Bold Tag in StringPremium	Trie, Array, Hash Table +2
0758	Bold Words in StringPremium	Trie, Array, Hash Table +2
1166	Design File SystemPremium	Design, Trie, Hash Table +1
1698	Number of Distinct Substrings in a StringPremium	Trie, String, Suffix Array +2
1804	Implement Trie II (Prefix Tree)Premium	Design, Trie, Hash Table +1
1858	Longest Word With All PrefixesPremium	Depth-First Search, Trie, Array +1

Hard (22)

Hard problems
No.	Problem	Topics
0140	Word Break II	Trie, Memoization, Array +4
0212	Word Search II	Trie, Array, String +2
0336	Palindrome Pairs	Trie, Array, Hash Table +1
0440	K-th Smallest in Lexicographical Order	Trie
0472	Concatenated Words	Depth-First Search, Trie, Array +3
0745	Prefix and Suffix Search	Design, Trie, Array +2
1032	Stream of Characters	Design, Trie, Array +2
1178	Number of Valid Words for Each Puzzle	Bit Manipulation, Trie, Array +2
1316	Distinct Echo Substrings	Trie, String, Hash Function +1
1707	Maximum XOR With an Element From Array	Bit Manipulation, Trie, Array
1803	Count Pairs With XOR in a Range	Bit Manipulation, Trie, Array
1948	Delete Duplicate Folders in System	Trie, Array, Hash Table +2
2227	Encrypt and Decrypt Strings	Design, Trie, Array +2
2416	Sum of Prefix Scores of Strings	Trie, Array, String +1
2935	Maximum Strong Pair XOR II	Bit Manipulation, Trie, Array +2
2977	Minimum Cost to Convert String II	Graph, Trie, Array +3
0425	Word SquaresPremium	Trie, Array, String +1
0527	Word AbbreviationPremium	Greedy, Trie, Array +2
0588	Design In-Memory File SystemPremium	Design, Trie, Hash Table +2
0642	Design Search Autocomplete SystemPremium	Depth-First Search, Design, Trie +4
1938	Maximum Genetic Difference Query	Bit Manipulation, Depth-First Search, Trie +2
2479	Maximum XOR of Two Non-Overlapping SubtreesPremium	Tree, Depth-First Search, Graph +1

Trie LeetCode Problems: All 49,
With Python Solutions

How Trie problems are solved

When the Trie problem arrives live.

Approach

Approach

Approach

Trie problems by difficulty

Easy (3)

Medium (24)

Hard (22)

Keep exploring

How Trie problems are solved

When the Trie problem arrives live.

Approach

Approach

Approach

Trie problems by difficulty

Easy (3)3

Medium (24)24

Hard (22)22

Keep exploring

Easy (3)

Medium (24)

Hard (22)