Graph

Detect Cycle in a Directed Graph.

class Solution {    boolean isCyclicUtil(int i, boolean[] visited, boolean[] recursionStack) {            // Mark the current node as visited and            // part of recursion stack            if (recursionStack[i]) return true;            if (visited[i]) return false;                    visited[i] = true;            recursionStack[i] = true;                    List<Integer> children = adj.get(i);            for (Integer c : children){                    if (isCyclicUtil(c, visited, recursionStack)){                        return true;                }            recursionStack[i] = false;            return false;        }        boolean isCyclic() {            // Mark all the vertices as not visited and            // not part of recursion stack            boolean[] visited = new boolean[V];            boolean[] recursionStack= new boolean[V];                    // Call the recursive helper function to            // detect cycle in different DFS trees            for (int i = 0; i < V; i++) if (                isCyclicUtil(i, visited, recursionStack)            ) return true;                    return false;        }}