java - Finding all hamiltonian cycles -

i'm trying implement method adding possible hamiltonian cycles list using recursion. far stopping condition isn't sufficient , "outofmemoryerror: java heap space" in line adds vertex list:

private boolean gethamiltoniancycles(int first, int v, int[] parent,         boolean[] isvisited, list<list<integer>> cycles) {     isvisited[v] = true;     if (allvisited(isvisited) && neighbors.get(v).contains(new integer(first))) {         arraylist<integer> cycle = new arraylist<>();         int vertex = v;         while (vertex != -1) {             cycle.add(vertex);             vertex = parent[vertex];         }         cycles.add(cycle);         return true;     } else if (allvisited(isvisited)) {         isvisited[v] = false;         return false;     }     boolean cycleexists = false;     (int = 0; < neighbors.get(v).size(); i++) {         int u = neighbors.get(v).get(i);         parent[u] = v;         if (!isvisited[u]                 && gethamiltoniancycles(first, u, parent, isvisited, cycles)) {             cycleexists = true;         }     }     //if (!cycleexists) {         isvisited[v] = false; // backtrack     //}     return cycleexists; } 

can please suggest me i'm doing wrong or approach incorrect?

edit: suggested in comments, culprit parent array, causing infinite loop. wasn't able correct , changed array store child element. seems work:

private boolean gethamiltoniancycles(int first, int v, int[] next,         boolean[] isvisited, list<list<integer>> cycles) {     isvisited[v] = true;     if (allvisited(isvisited) && neighbors.get(v).contains(first)) {         arraylist<integer> cycle = new arraylist<>();         int vertex = first;         while (vertex != -1) {             cycle.add(vertex);             vertex = next[vertex];         }         cycles.add(cycle);         isvisited[v] = false;         return true;     }     boolean cycleexists = false;     (int u : neighbors.get(v)) {         next[v] = u;         if (!isvisited[u]                 && gethamiltoniancycles(first, u, next, isvisited, cycles)) {             cycleexists = true;         }     }      next[v] = -1;     isvisited[v] = false; // backtrack     return cycleexists; } 

if looking disjoint hamiltonian cycles here have implementation using backtracking.