207. Course Schedule

解題說明

C++ 解法

複雜度分析

虛擬碼

1. Build adjacency list from prerequisites
2. Initialize state[0..n-1] = 0 (unvisited)
3. For each node i:
   a. Run DFS: if state[i]==1 → cycle; if state[i]==2 → skip
   b. Mark state[i]=1 (visiting), recurse on neighbors, mark state[i]=2
4. Return true if no cycle found

其他解法

延伸思考