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g2301_2400.s2360_longest_cycle_in_a_graph.Solution Maven / Gradle / Ivy

package g2301_2400.s2360_longest_cycle_in_a_graph;

// #Hard #Depth_First_Search #Graph #Topological_Sort
// #2022_08_14_Time_37_ms_(90.19%)_Space_102.8_MB_(72.92%)

public class Solution {
    public int longestCycle(int[] edges) {
        int n = edges.length;
        boolean[] vis = new boolean[n];
        boolean[] dfsvis = new boolean[n];
        int[] path = new int[n];
        int maxLength = -1;
        for (int i = 0; i < n; i++) {
            if (!vis[i]) {
                path[i] = 1;
                maxLength = Math.max(maxLength, dfs(i, 1, path, vis, dfsvis, edges));
            }
        }
        return maxLength;
    }

    private int dfs(
            int node, int pathLength, int[] path, boolean[] vis, boolean[] dfsvis, int[] edges) {
        vis[node] = true;
        dfsvis[node] = true;
        int length = -1;
        if (edges[node] != -1 && !vis[edges[node]]) {
            path[edges[node]] = pathLength + 1;
            length = dfs(edges[node], pathLength + 1, path, vis, dfsvis, edges);
        } else if (edges[node] != -1 && dfsvis[edges[node]]) {
            length = pathLength - path[edges[node]] + 1;
        }
        dfsvis[node] = false;
        return length;
    }
}