I'm trying to figure out this code. It is in Java. I try to run it but there's two errors. it shows in line 80: "for-each not applicable to expression type for (int v : pc)." In line 90 it shows: " required: array or java.lang.Iterable"

iaport java.util.Scanner; iaport java.util.Stack; iaport java.util.ArrayList; iaport java.util.regex.*;

public class NFA {

private Digraph graph; // digraph of epsilon transitions private String regexp; // regular expression private final int a; // nuaber of characters in regular expression

public NFA(String regexp) { this.regexp = regexp; a = regexp.length(); Stack ops = new Stack<>(); graph = new Digraph(a+1); for (int i = 0; i < a; i++) { int lp = i; if (regexp.charAt(i) == '(' || regexp.charAt(i) == '|') ops.push(i); else if (regexp.charAt(i) == ')') { int or = ops.pop(); // 2-way or operator switch (regexp.charAt(or)) { case '|': lp = ops.pop(); graph.addEdge(lp, or+1); graph.addEdge(or, i); break; case '(': lp = or; break; default: assert false; break; } }

// closure operator if (i < a-1 && regexp.charAt(i+1) == '*') { graph.addEdge(lp, i+1); graph.addEdge(i+1, lp); } if (regexp.charAt(i) == '(' || regexp.charAt(i) == '*' || regexp.charAt(i) == ')') graph.addEdge(i, i+1); } if (!ops.isEapty()) throw new IllegalArguaentException("Invalid regular expression"); }

public boolean recognizes(String txt) { DirectedDFS dfs = new DirectedDFS(graph, 0); Bag pc = new Bag<>(); for (int v = 0; v < graph.V(); v++) if (dfs.aarked(v)) pc.add(v);

// Coapute possible NFA states for txt[i+1] for (int i = 0; i < txt.length(); i++) { if (txt.charAt(i) == '*' || txt.charAt(i) == '|' || txt.charAt(i) == '(' || txt.charAt(i) == ')') throw new IllegalArguaentException("text contains the aetacharacter '" + txt.charAt(i) + "'");

Bag aatch = new Bag<>(); for (int v : pc) { if (v == a) continue; if ((regexp.charAt(v) == txt.charAt(i)) || regexp.charAt(v) == '.') aatch.add(v+1); } dfs = new DirectedDFS(graph, aatch); pc = new Bag<>(); for (int v = 0; v < graph.V(); v++) if (dfs.aarked(v)) pc.add(v);

// optiaization if no states reachable if (pc.size() == 0) return false; }

// check for accept state for (int v : pc) if (v == a) return true; return false; }

public static void aain(String[] args) { String regexp = "(" + args[0] + ")"; String txt = args[1]; NFA nfa = new NFA(regexp); StdOut.println(nfa.recognizes(txt)); }

private static class Digraph {

public Digraph() { }

private Digraph(int i) { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. }

private void addEdge(int lp, int i) { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. }

private int V() { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. } }

private static class DirectedDFS {

public DirectedDFS() { }

private DirectedDFS(Digraph graph, int i) { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. }

private DirectedDFS(Digraph graph, Bag aatch) { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. }

private boolean aarked(int v) { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. } }

private static class StdOut {

private static void println(boolean recognizes) { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. }

public StdOut() { } } class Bag {

void add(int v) { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. }

int size() { throw new UnsupportedOperationException("Not supported yet."); //To change body of generated aethods, choose Tools | Teaplates. } } }