dsa1 min read
All Paths Source to Target — DFS Backtracking
Find all paths from node 0 to node n-1 in a DAG. DFS with backtracking: explore each path, add to results when destination reached.
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dsa1 min read
Network Delay Time — Dijkstra Shortest Paths
Find time for signal to reach all nodes. Single-source shortest path (Dijkstra) from node k; answer is max of all shortest distances.
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dsa1 min read
Cheapest Flights Within K Stops — Bellman-Ford / BFS
Find cheapest flight from src to dst with at most k stops. Bellman-Ford with k+1 iterations or BFS level-by-level.
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dsa2 min read
Word Ladder — BFS Shortest Transformation
Find minimum transformations from beginWord to endWord changing one letter at a time (each intermediate must be in wordList). Classic BFS on word states.
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Word Ladder II — BFS Shortest Paths + DFS Reconstruct
Find ALL shortest transformation sequences. BFS builds layer map, DFS reconstructs all paths backwards from endWord to beginWord.
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