LeetCode ·

LeetCode 851: Loud and Rich

2026-04-13·2 mins

LeetCode Medium Graph Topological-Sort

LeetCode note for Loud and Rich, rebuilt from the original learning note

LeetCode 802: Find Eventual Safe States

2026-04-13·3 mins

LeetCode Medium Graph Topological-Sort

LeetCode note for Find Eventual Safe States, rebuilt from the original learning note

LeetCode 1203: Sort Items by Groups Respecting Dependencies

2026-04-13·3 mins

LeetCode Hard Graph Topological-Sort

LeetCode note for Sort Items by Groups Respecting Dependencies, rebuilt from the original learning note

LeetCode 3900: Longest Balanced Substring After One Swap

2026-04-12·3 mins

LeetCode Medium Prefix-Sum Hash-Table String

LeetCode 3900 note: equal prefix differences mean balanced; a substring off by 2 also works if a swappable character exists outside, and keeping the two earliest positions per difference is enough

LeetCode 3899: Angles of a Triangle

2026-04-12·2 mins

LeetCode Medium Math Geometry

LeetCode 3899 note: check the triangle inequality first, compute the three angles with the law of cosines, and remember to sort them

LeetCode 3898: Find the Degree of Each Vertex

2026-04-12·1 min

LeetCode Easy Graph Matrix Array

LeetCode 3898 note: the number of ones in row i of the adjacency matrix is vertex i’s degree

LeetCode 310: Minimum Height Trees

2026-04-11·3 mins

LeetCode Medium Graph Topological-Sort

LeetCode note for Minimum Height Trees, rebuilt from the original learning note

LeetCode 2115: Find All Possible Recipes from Given Supplies

2026-04-11·3 mins

LeetCode Medium Graph Topological-Sort

LeetCode note for Find All Possible Recipes from Given Supplies, rebuilt from the original learning note

LeetCode 2192: All Ancestors of a Node in a DAG

2026-04-08·3 mins

LeetCode Medium Graph Topological-Sort

LeetCode note for All Ancestors of a Node in a DAG, rebuilt from the original learning note

LeetCode 210: Course Schedule II

2026-04-08·2 mins

LeetCode Medium Graph Topological-Sort

LeetCode note for Course Schedule II, rebuilt from the original learning note

LeetCode 207: Course Schedule

2026-04-08·2 mins

LeetCode Medium Graph Topological-Sort

LeetCode note for Course Schedule, rebuilt from the original learning note

LeetCode 1971: Find if Path Exists in Graph

2026-04-08·2 mins

LeetCode Easy Graph Union-Find

LeetCode note for Find if Path Exists in Graph, rebuilt from the original learning note