Shortest Path LeetCode Problems: 27 Python Solutions

Shortest Path problems by difficulty

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

Medium (15)

Medium problems
No.	Problem	Topics
0399	Evaluate Division	Depth-First Search, Breadth-First Search, Union Find +4
0743	Network Delay Time	Depth-First Search, Breadth-First Search, Graph +2
0787	Cheapest Flights Within K Stops	Depth-First Search, Breadth-First Search, Graph +3
1334	Find the City With the Smallest Number of Neighbors at a Threshold Distance	Graph, Dynamic Programming, Shortest Path
1514	Path with Maximum Probability	Graph, Array, Shortest Path +1
1786	Number of Restricted Paths From First to Last Node	Graph, Topological Sort, Dynamic Programming +2
1976	Number of Ways to Arrive at Destination	Graph, Topological Sort, Dynamic Programming +1
2662	Minimum Cost of a Path With Special Roads	Graph, Array, Shortest Path +1
2976	Minimum Cost to Convert String I	Graph, Array, String +1
0505	The Maze IIPremium	Depth-First Search, Breadth-First Search, Graph +4
1810	Minimum Path Cost in a Hidden GridPremium	Depth-First Search, Breadth-First Search, Graph +5
2093	Minimum Cost to Reach City With DiscountsPremium	Graph, Shortest Path, Heap (Priority Queue)
2297	Jump Game VIIIPremium	Stack, Graph, Array +3
2473	Minimum Cost to Buy ApplesPremium	Graph, Array, Shortest Path +1
2737	Find the Closest Marked NodePremium	Graph, Array, Shortest Path +1

Hard (12)

Hard problems
No.	Problem	Topics
0882	Reachable Nodes In Subdivided Graph	Graph, Shortest Path, Heap (Priority Queue)
1368	Minimum Cost to Make at Least One Valid Path in a Grid	Breadth-First Search, Graph, Array +3
2045	Second Minimum Time to Reach Destination	Breadth-First Search, Graph, Shortest Path
2203	Minimum Weighted Subgraph With the Required Paths	Graph, Shortest Path
2290	Minimum Obstacle Removal to Reach Corner	Breadth-First Search, Graph, Array +3
2577	Minimum Time to Visit a Cell In a Grid	Breadth-First Search, Graph, Array +3
2642	Design Graph With Shortest Path Calculator	Graph, Design, Shortest Path +1
2699	Modify Graph Edge Weights	Graph, Shortest Path, Heap (Priority Queue)
2959	Number of Possible Sets of Closing Branches	Bit Manipulation, Graph, Enumeration +2
2977	Minimum Cost to Convert String II	Graph, Trie, Array +3
0499	The Maze IIIPremium	Depth-First Search, Breadth-First Search, Graph +5
2714	Find Shortest Path with K HopsPremium	Graph, Shortest Path, Heap (Priority Queue)

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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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GPT-6.1 Terra

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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...

GPT-6.1 TerraClear chat

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

90%Subscription

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+

Shortest Path LeetCode Problems: All 27,
With Python Solutions

Shortest Path problems by difficulty

Medium (15)

Hard (12)

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Shortest Path problems by difficulty

Medium (15)15

Hard (12)12

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Medium (15)

Hard (12)