Save New Duplicate & Edit Just Text Twitter
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package app;

import java.io.*;
import java.util.*;
import java.util.regex.*;

import structures.Stack;

public class Expression {

    public static String delims = " \t*+-/()[]";

    /**
     * Populates the vars list with simple variables, and arrays lists with arrays
     * in the expression. For every variable (simple or array), a SINGLE instance is created
     * and stored, even if it appears more than once in the expression.
     * At this time, values for all variables and all array items are set to
     * zero - they will be loaded from a file in the loadVariableValues method.
     *
     * @param expr The expression
     * @param vars The variables array list - already created by the caller
     * @param arrays The arrays array list - already created by the caller
     */
    public static void
    makeVariableLists(String expr, ArrayList<Variable> vars, ArrayList<Array> arrays) {
        /** COMPLETE THIS METHOD **/
        /** DO NOT create new vars and arrays - they are already created before being sent in
         ** to this method - you just need to fill them in.
         **/
        System.out.println(vars+"VAR | ARR"+arrays); //vars and arrays are already created but empty///// can delete after code done

        String exprNew = expr.trim(), currentItem;

        String delims2 = " \t*+-/()";
        StringTokenizer st = new StringTokenizer(exprNew,delims2);

        while(st.hasMoreTokens()){
            currentItem = st.nextToken();

             if ( currentItem.contains("[") ){
                int ArrNameStartingIndex = 0;
                boolean duplicateA = false;

                for (int j = 0; j < currentItem.length(); j ++) {

                    if (currentItem.charAt(j)== '[') {

                        if (arrays.size() == 0) {
                                arrays.add( new Array(currentItem.substring(ArrNameStartingIndex,j)) );
                                ArrNameStartingIndex = j + 1;

                        }else if (arrays.size() != 0) {
                            for (int k = 0; k < arrays.size(); k++) {
                                if (arrays.get(k).name.contentEquals(  currentItem.substring(ArrNameStartingIndex,j) ) ) {
                                    ArrNameStartingIndex = j + 1;
                                    duplicateA = true;
                                }
                            }
                            if (duplicateA == false) {
                                arrays.add( new Array(currentItem.substring(ArrNameStartingIndex,j)) );
                                ArrNameStartingIndex = j + 1;
                            }
                        }
                     }else {
                         continue;
                     }
                 }

             }else if ( currentItem.matches("^[a-zA-Z]*$") ) {

                 //set duplicate boolean to false each time a possible variable is found
                 boolean duplicateV = false;

                 //if variablelist is empty, need not worry about duplicates
                 if (vars.size() == 0) {
                     vars.add( new Variable(currentItem) );

                // if variablelist has items, check each of them with current possible variable
                     // if no matches found, add current p. var into list
                 }else{
                     for (int k = 0; k < vars.size(); k++) {
                            if (vars.get(k).name.contentEquals(currentItem) ) {
                                duplicateV = true;
                            }
                    }
                     if(duplicateV == false) {
                        vars.add(new Variable(currentItem));
                    }
                 }

             }else {
                 continue;
             }

        }

        System.out.println(vars+"VAR | ARR"+arrays); // vars and arrays should now be filled/////
    }

    /**
     * Loads values for variables and arrays in the expression
     *
     * @param sc Scanner for values input
     * @throws IOException If there is a problem with the input
     * @param vars The variables array list, previously populated by makeVariableLists
     * @param arrays The arrays array list - previously populated by makeVariableLists
     */
    public static void
    loadVariableValues(Scanner sc, ArrayList<Variable> vars, ArrayList<Array> arrays)
    throws IOException {
        while (sc.hasNextLine()) {
            StringTokenizer st = new StringTokenizer(sc.nextLine().trim());
            int numTokens = st.countTokens();
            String tok = st.nextToken();
            Variable var = new Variable(tok);
            Array arr = new Array(tok);
            int vari = vars.indexOf(var);
            int arri = arrays.indexOf(arr);
            if (vari == -1 && arri == -1) {
                continue;
            }
            int num = Integer.parseInt(st.nextToken());
            if (numTokens == 2) { // scalar symbol
                vars.get(vari).value = num;
            } else { // array symbol
                arr = arrays.get(arri);
                arr.values = new int[num];
                // following are (index,val) pairs
                while (st.hasMoreTokens()) {
                    tok = st.nextToken();
                    StringTokenizer stt = new StringTokenizer(tok," (,)");
                    int index = Integer.parseInt(stt.nextToken());
                    int val = Integer.parseInt(stt.nextToken());
                    arr.values[index] = val;
                }
            }
        }
    }

    /**
     * Evaluates the expression.
     *
     * @param vars The variables array list, with values for all variables in the expression
     * @param arrays The arrays array list, with values for all array items
     * @return Result of evaluation
     */
    public static float
    evaluate(String expr, ArrayList<Variable> vars, ArrayList<Array> arrays) {
        /** COMPLETE THIS METHOD **/
        String currentItem = "";


        // builds expr array list // treat brackets as letters
        ArrayList<String> exprArrL = new ArrayList<>();
        String matchSet = "[a-zA-Z0-9\\[\\]]*";

        String prev = Character.toString(expr.charAt(0));
        String current = "";
        currentItem += prev;

        for (int i = 1; i < expr.length(); i ++) {

            current = Character.toString(expr.charAt(i));

            //CHARACTER1prev is letter + CHARACTER2curris letter
            if ( current.matches(matchSet) && current.matches(matchSet) ) {

                currentItem += current;
                prev = current;

            //CHARACTER1prev is not letter(operator or parenthesis or bracket) + CHARACTER2curr is letter
            }else if ( current.matches(matchSet) && !current.matches(matchSet)) {

                currentItem += current;
                prev = current;

            //current is not letter(operator or parenthesis or bracket)
            }else if ( !current.matches(matchSet) )  {

                if (currentItem!= "") {
                    exprArrL.add(currentItem);
                }
                currentItem = "";
                exprArrL.add(current);
                prev = current;
            }
        }
        if (currentItem!= "") {
            exprArrL.add(currentItem);
        }

        // exprArrList done building / can now evaluate/////////////////////////////////////////////////////

        Stack<String> operators = new Stack<String>();
        Stack<Integer> numbers = new Stack<Integer>();



            for (int x = 0; x < exprArrL.size(); x++) {

                currentItem = exprArrL.get(x);


                if ( currentItem.equals("(") ) {
                operators.push(currentItem);

                }else if (currentItem.equals(")")) {
                      if (!operators.peek().equals("(") ) {
                         numbers.push(applyOperation(operators.pop(), numbers.pop(), numbers.pop()));
                         operators.pop();
                       }

                      //array needs evaluation before push
                }else if ( currentItem.contains("[") ){
                    currentItem = Integer.toString(convertArray(currentItem, arrays, vars)) ;
                    pushNum(currentItem,vars,numbers);

                    // push operator into ops stack
                }else if (currentItem.equals( "+") || currentItem.equals( "-" )|| currentItem.equals( "*" )|| currentItem.equals( "/")) {
                       // While top of 'ops' has same or greater precedence to current
                       // token, which is an operator. Apply operator on top of 'ops'
                       // to top two elements in values stack
                       while (!operators.isEmpty() && hasPrecedence(currentItem, operators.peek()))
                           numbers.push(applyOperation(operators.pop(), numbers.pop(), numbers.pop()));

                       // Push current token to 'ops'.
                       operators.push(currentItem);

                       //variable or num, can be pushed in
                }else {
                    pushNum(currentItem,vars,numbers);

                }

            }
            while (!operators.isEmpty())
                numbers.push(applyOperation(operators.pop(), numbers.pop(), numbers.pop()));

            // Top of 'values' contains result, return it
            return numbers.pop();

        }



    private static void pushNum(String currentItem, ArrayList<Variable> vars, Stack<Integer> numbers ) {

        //variable -push num value
        if (currentItem.matches("^[a-zA-Z]*$")){
            for(int v = 0; v < vars.size() ; v ++) {
                if (vars.get(v).name.contentEquals( currentItem ) ) {
                    numbers.push(vars.get(v).value);
                }
            }

        //is a number - push num value
        }else{
            numbers.push(Integer.parseInt(currentItem));
        }
    }

    private static int convertArray(String inputArrayStr0, ArrayList<Array> arrays, ArrayList<Variable> vars ) {
        int ans = 0;

        while (inputArrayStr0.contains("[") ) {
            int starti = 0, endi = 0, lenName = 0;

            inputArrayStr0 += " ";

            for (int s = 0; s<inputArrayStr0.length(); s++) {
                if ( Character.isLetter(inputArrayStr0.charAt(s) ) ||  Character.isDigit(inputArrayStr0.charAt(s) ) ){
                    lenName++;
                }else if (inputArrayStr0.charAt(s) == '[') {
                    starti = s-lenName;
                    lenName = 0;
                }else if (inputArrayStr0.charAt(s) == ']') {
                    endi = s+1;
                    break;
                }
            }

            String inputArrayStr =  inputArrayStr0.substring(starti,endi);
            String inputArrayName = "";
            String currentItem = "";

            /////////////////////////////////////gggggggggggggggggggggggggg
            if (inputArrayStr.contains("(") ){
                Stack<String> operators = new Stack<String>();
                Stack<Integer> numbers = new Stack<Integer>();

                StringTokenizer st = new StringTokenizer(inputArrayStr,"");

                    while (st.hasMoreTokens()) {
                        currentItem = st.nextToken();

                        if (currentItem.equals( "+") || currentItem.equals( "-" )|| currentItem.equals( "*" )|| currentItem.equals( "/")) {
                           // While top of 'ops' has same or greater precedence to current
                           // token, which is an operator. Apply operator on top of 'ops'
                           // to top two elements in values stack
                           while (!operators.isEmpty() && hasPrecedence(currentItem, operators.peek())) {
                               numbers.push(applyOperation(operators.pop(), numbers.pop(), numbers.pop()));

                           // Push current token to 'ops'.
                           operators.push(currentItem);
                           }

                       //variable or num, can be pushed in
                        }else {
                            pushNum(currentItem,vars,numbers);
                        }
                    }
                    while (!operators.isEmpty())
                        numbers.push(applyOperation(operators.pop(), numbers.pop(), numbers.pop()));

                    int result = numbers.pop();

                }




            // take in something like "b[0]"
            int start = 0, end = 0;
            String numberInBracketS = "";
            int numberInBracket = 0;

            //////////////////////////////////////////////////////////evaluates innermost b[0]
            for (int i = 0; i<inputArrayStr.length(); i++) {
                if (inputArrayStr.charAt(i) == '[') {
                    start = i + 1;
                }
                if (inputArrayStr.charAt(i) == ']') {
                    end = i;
                }
            }
            numberInBracketS = inputArrayStr.substring(start,end);
            numberInBracket = Integer.parseInt(numberInBracketS);
            inputArrayName = inputArrayStr.substring(0,start-1);

            for (int a = 0; a < arrays.size() ; a ++) {
                if (arrays.get(a).name.equals(inputArrayName) ){
                            ans = arrays.get(a).values[numberInBracket];
                }
            }
            ///////////////////////////////////////////////////////////////

            inputArrayStr0= inputArrayStr0.replace(inputArrayStr,Integer.toString(ans));
        }
        return ans;
    }

    private static int applyOperation(String op, int  b, int a) {


        switch (op)
        {
        case "+":
            return a + b;
        case "-":
            return a - b;
        case "*":
            return a * b;
        case "/":
            if (b == 0)
                throw new
                UnsupportedOperationException("Cannot divide by zero");
            return a / b;
        }
        return 0;
    }

    private static boolean hasPrecedence(String op1, String op2)
    {
        if (op2.equals("(") || op2.equals( ")"))
            return false;
        if ((op1.equals( "*") || op1.equals( "/")) && (op2.equals( "+" )|| op2.equals( "-")) )
            return false;
        else
            return true;
    }
}