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// 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);
}
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