LeetCode 2976 | Minimum Cost to Convert String I | Java | Medium | Shortest Path | CodeByTushu
Description: π Welcome Back to CodeByTushu!
In todayβs video, we solve LeetCode 2976 β Minimum Cost to Convert String I using Graph & Floyd-Warshall Algorithm in Java.
We are given two strings, source and target, along with character transformation rules and their associated costs. Our goal is to determine the minimum cost to convert source into target, or return -1 if any character transformation is impossible. Because each character position can be transformed independently, the global problem breaks down into finding the shortest path between every pair of characters in a directed graph. With only 26 lowercase English letters, the number of vertices is small and fixed at 26.
We model the transformation rules as a directed weighted graph with 26 nodes and run the Floyd-Warshall algorithm to compute all-pairs shortest paths in O(26^3) = 17,576 operations. Duplicate transition rules between the same pair of characters are resolved by taking the minimum edge cost. Once the 26 x 26 all-pairs shortest distance matrix is precomputed, we iterate through the strings in O(n) time, accumulating the minimal transformation costs using 64-bit integers to prevent integer overflow.
π₯ Problem Highlights
β Character conversions are independent across string positions
β Small alphabet size (|Ξ£| = 26) makes all-pairs shortest path optimal
β Floyd-Warshall precomputes shortest paths between all 26 letters in O(26^3)
β Safely handles multi-hop conversions and duplicate transformation rules
β Uses 64-bit long accumulator to avoid integer overflow on large strings
β Time Complexity: O(|Ξ£|^3 + |E| + N) | Auxiliary Space Complexity: O(|Ξ£|^2) = O(1)
β±οΈ TIMESTAMPS
00:00 Intro
00:51 Problem Understanding
01:41 Key Observation
03:06 Floyd-Warshall APSP Approach
04:22 Java Code Walkthrough
05:24 Execution & Test Cases
06:24 Time Complexity Analysis
07:09 Space Complexity Analysis
07:44 Outro & Wrap-up
π Problem Folder & Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I
β Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I/Solution.java
π Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I/solution.py
β‘ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I/solution.cpp
π JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I/solution.js
π LeetCode Source Code
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π₯ Perfect For
LeetCode Medium Problems
Java DSA Preparation
Graph Shortest Path
Floyd-Warshall Algorithm
String Manipulation
Time Complexity Optimization
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π¬ Question of the Day
Why is Floyd-Warshall preferred over running Dijkstra 26 times for LeetCode 2976?
1οΈβ£ Dijkstra cannot handle directed graphs
2οΈβ£ With only 26 vertices, Floyd-Warshall takes only 26^3 = 17,576 operations with simpler implementation and zero priority queue overhead
3οΈβ£ Floyd-Warshall works only when negative cycles exist
4οΈβ£ Dijkstra requires O(N) space where N is the length of the string
#LeetCode2976 #LeetCode #MinimumCostToConvertStringI #Java #JavaDSA #FloydWarshall #Graph #ShortestPath #DSA #CodingInterview #ProblemSolving #LeetCodeMedium #DailyLeetCode #JavaProgramming #CodeByTushu
π Comment the answer below! π₯Β Close description
In todayβs video, we solve LeetCode 2976 β Minimum Cost to Convert String I using Graph & Floyd-Warshall Algorithm in Java.
We are given two strings, source and target, along with character transformation rules and their associated costs. Our goal is to determine the minimum cost to convert source into target, or return -1 if any character transformation is impossible. Because each character position can be transformed independently, the global problem breaks down into finding the shortest path between every pair of characters in a directed graph. With only 26 lowercase English letters, the number of vertices is small and fixed at 26.
We model the transformation rules as a directed weighted graph with 26 nodes and run the Floyd-Warshall algorithm to compute all-pairs shortest paths in O(26^3) = 17,576 operations. Duplicate transition rules between the same pair of characters are resolved by taking the minimum edge cost. Once the 26 x 26 all-pairs shortest distance matrix is precomputed, we iterate through the strings in O(n) time, accumulating the minimal transformation costs using 64-bit integers to prevent integer overflow.
π₯ Problem Highlights
β Character conversions are independent across string positions
β Small alphabet size (|Ξ£| = 26) makes all-pairs shortest path optimal
β Floyd-Warshall precomputes shortest paths between all 26 letters in O(26^3)
β Safely handles multi-hop conversions and duplicate transformation rules
β Uses 64-bit long accumulator to avoid integer overflow on large strings
β Time Complexity: O(|Ξ£|^3 + |E| + N) | Auxiliary Space Complexity: O(|Ξ£|^2) = O(1)
β±οΈ TIMESTAMPS
00:00 Intro
00:51 Problem Understanding
01:41 Key Observation
03:06 Floyd-Warshall APSP Approach
04:22 Java Code Walkthrough
05:24 Execution & Test Cases
06:24 Time Complexity Analysis
07:09 Space Complexity Analysis
07:44 Outro & Wrap-up
π Problem Folder & Detailed Documentation:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/tree/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I
β Java Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I/Solution.java
π Python Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I/solution.py
β‘ C++ Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I/solution.cpp
π JavaScript Solution:
https://github.com/CodeByTushu/CodeByTushu-LeetCode-Solutions/blob/main/solutions/January/29-January/2976-Minimum-Cost-to-Convert-String-I/solution.js
π LeetCode Source Code
π Admin type the link
π All LeetCode Solutions
π https://codebytushu.com/Leetcode/
π± Join CodeByTushu on WhatsApp
Get coding updates, LeetCode solutions, daily questions and more.
https://whatsapp.com/channel/0029Vb8k5mCDeON2Xwlkxe40
β€οΈ Donate
π https://codebytushu.com/Leetcode/donate.php
π₯ Perfect For
LeetCode Medium Problems
Java DSA Preparation
Graph Shortest Path
Floyd-Warshall Algorithm
String Manipulation
Time Complexity Optimization
Coding Interview Preparation
Problem Solving
π Follow CodeByTushu
βΆοΈ YouTube: https://www.youtube.com/@codebytushu
πΈ Instagram: https://instagram.com/codebytushu/
πΌ LinkedIn: https://www.linkedin.com/company/codebytushu/
π Website: https://codebytushu.com
π GitHub: https://github.com/CodeByTushu
β€οΈ Donβt Forget To
π Like | π¬ Comment | π Subscribe
π¬ Question of the Day
Why is Floyd-Warshall preferred over running Dijkstra 26 times for LeetCode 2976?
1οΈβ£ Dijkstra cannot handle directed graphs
2οΈβ£ With only 26 vertices, Floyd-Warshall takes only 26^3 = 17,576 operations with simpler implementation and zero priority queue overhead
3οΈβ£ Floyd-Warshall works only when negative cycles exist
4οΈβ£ Dijkstra requires O(N) space where N is the length of the string
#LeetCode2976 #LeetCode #MinimumCostToConvertStringI #Java #JavaDSA #FloydWarshall #Graph #ShortestPath #DSA #CodingInterview #ProblemSolving #LeetCodeMedium #DailyLeetCode #JavaProgramming #CodeByTushu
π Comment the answer below! π₯Β Close description