802. Find Eventual Safe States
https://leetcode.com/problems/find-eventual-safe-states/description/
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | class Solution { public : vector< bool > visited; vector< int > mem; // -1 unknown, 0 unsafe, 1 safe. int n; vector< int > eventualSafeNodes(vector<vector< int >>& graph) { n = graph.size(); mem = vector< int >(n, -1); visited = vector< bool >(n, false ); for ( int i = 0; i < n; i++) dfs(graph, i); vector< int > res; for ( int i = 0; i < n; i++) if (mem[i] == 1) res.push_back(i); return res; } bool dfs(vector<vector< int >>& graph, int i) { // check if i is evetually safe if (mem[i] != -1) return mem[i] == 1; bool res = true ; if (visited[i]) { // A loop res = false ; } else { visited[i] = true ; for (auto j : graph[i]) { if (!dfs(graph, j)) { res = false ; break ; } } // visited[i] = false; <strong>// This line is optional, since we've cached the result for i in mem.</strong> } mem[i] = res; return res; } }; |
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