// 802. Find Eventual Safe States #include "leetcode.h" /* * there is a directed graph of 'n' nodes with each node labeled from 0 to n * - 1. the graph is represented by a 0-indexed 2d integer array 'graph' where * 'graph[i]' is an integer array of nodes adjacent to node 'i', meaning there * is an edge from node 'i' to each node in 'graph[i]'. a node is a terminal * node if there are no outgoing edges. a node is a safe node if every possible * path starting from that node leads to a terminal node ( or another safe * node). return an array containing all the safe nodes of the graph. the answer * should be sorted in ascending order. */ bool dfs(int **graph, int graphSize, int *graphColSize, int *vis, int node) { if (vis[node] == 1) return true; if (vis[node] == 2) return false; vis[node] = 2; for (int i = 0; i < graphColSize[node]; i++) if (!dfs(graph, graphSize, graphColSize, vis, graph[node][i])) return false; vis[node] = 1; return true; } int *eventualSafeNodes(int **graph, int graphSize, int *graphColSize, int *returnSize) { int n = graphSize, idx = 0; int *vis = (int *)calloc(n, sizeof(int)); int *ans = (int *)malloc(n * sizeof(int)); for (int i = 0; i < n; i++) if (dfs(graph, graphSize, graphColSize, vis, i)) { ans[idx] = i; idx++; } free(vis); *returnSize = idx; ans = (int *)realloc(ans, idx * sizeof(int)); return ans; } int main() { int g1i[7][2] = {{1, 2}, {2, 3}, {5}, {0}, {5}, {}, {}}, rs1; int g2i[5][4] = {{1, 2, 3, 4}, {1, 2}, {3, 4}, {0, 4}, {}}, rs2; struct two_d_arr g1, g2; two_d_arr_init(&g1, ARRAY_SIZE(g1i), ARRAY_SIZE(g1i[0]), g1i); two_d_arr_init(&g2, ARRAY_SIZE(g2i), ARRAY_SIZE(g2i[0]), g2i); int *esn1 = eventualSafeNodes(g1.arr, g1.row_size, g1.col_size, &rs1); int *esn2 = eventualSafeNodes(g2.arr, g2.row_size, g2.col_size, &rs2); for (int i = 0; i < rs1; i++) printf("%d ", esn1[i]); // expect: 2 4 5 6 printf("\n"); for (int i = 0; i < rs2; i++) printf("%d ", esn2[i]); // expect: 4 printf("\n"); free(esn2), free(esn2); two_d_arr_free(&g1); two_d_arr_free(&g2); }