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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "---\n",
+    "title: FRQ 3\n",
+    "description: Third FRQ for collegeboard FRQ final\n",
+    "toc: true\n",
+    "layout: post\n",
+    "courses: { ToC: {week: 23} }\n",
+    "---"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 43,
+   "metadata": {
+    "vscode": {
+     "languageId": "java"
+    }
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "1 4 4\n",
+      "2 0 1\n",
+      "3 1 -9\n",
+      "1 1 5\n",
+      "new col3\n",
+      "2 0 1\n",
+      "1 3 4\n"
+     ]
+    }
+   ],
+   "source": [
+    "public class Main{\n",
+    "    public static void main (String args[]){\n",
+    "        SparseArray arr = new SparseArray();\n",
+    "        // System.out.println(arr.getValueAt(3, 1));\n",
+    "        arr.printEntries();\n",
+    "        arr.removeColumn(1);\n",
+    "        arr.printEntries();\n",
+    "        // System.out.println(arr.getValueAt(3, 1));\n",
+    "        // System.out.println(arr.getValueAt(1, 3));\n",
+    "    }\n",
+    "}\n",
+    "\n",
+    "public class SparseArrayEntry{\n",
+    "    private int row;\n",
+    "    private int col;\n",
+    "    private int value;\n",
+    "\n",
+    "    public SparseArrayEntry(int r, int c, int v){\n",
+    "        row = r;\n",
+    "        col = c;\n",
+    "        value = v;\n",
+    "    }\n",
+    "    public int getRow(){\n",
+    "        return row;\n",
+    "    }\n",
+    "\n",
+    "    public int getCol(){\n",
+    "        return col;\n",
+    "    }\n",
+    "\n",
+    "    public int getValue(){\n",
+    "        return value;\n",
+    "    }\n",
+    "}\n",
+    "\n",
+    "public class SparseArray{\n",
+    "    private int numRows;\n",
+    "    private int numCols;\n",
+    "    private List<SparseArrayEntry> entries;\n",
+    "\n",
+    "    public SparseArray(){\n",
+    "        entries = new ArrayList<SparseArrayEntry>();\n",
+    "        entries.add(new SparseArrayEntry(1, 4, 4));\n",
+    "        entries.add(new SparseArrayEntry(2, 0, 1));\n",
+    "        entries.add(new SparseArrayEntry(3, 1, -9));\n",
+    "        entries.add(new SparseArrayEntry(1, 1, 5));\n",
+    "    }\n",
+    "\n",
+    "    public int getNumRows(){\n",
+    "        return numRows;\n",
+    "    }\n",
+    "\n",
+    "    public int getNumCols(){\n",
+    "        return numCols;\n",
+    "    }\n",
+    "\n",
+    "    public int getValueAt(int row, int col){\n",
+    "        for (SparseArrayEntry e : entries){\n",
+    "            if (e.getRow() == row && e.getCol() == col){\n",
+    "                return e.getValue();\n",
+    "            }\n",
+    "        }\n",
+    "        return 0;\n",
+    "    }\n",
+    "\n",
+    "    public void printEntries(){\n",
+    "        for (SparseArrayEntry e : entries){\n",
+    "            System.out.println(String.valueOf(e.getRow()) + \" \" + String.valueOf(e.getCol()) + \" \" + String.valueOf(e.getValue()));\n",
+    "        }\n",
+    "    }\n",
+    "\n",
+    "    public void removeColumn(int col){\n",
+    "        numCols --;\n",
+    "        ArrayList<SparseArrayEntry> removeList = new ArrayList<SparseArrayEntry>();\n",
+    "        int iterator = entries.size();\n",
+    "        for (int i = 0; i < iterator; i ++){\n",
+    "            if (entries.get(i).getCol() == col){\n",
+    "                removeList.add(entries.get(i));\n",
+    "            }\n",
+    "            else if (entries.get(i).getCol() > col){\n",
+    "                System.out.println(\"new col\" + String.valueOf(entries.get(i).getCol() - 1));\n",
+    "                entries.add(new SparseArrayEntry(entries.get(i).getRow(), entries.get(i).getCol() - 1, entries.get(i).getValue()));\n",
+    "                removeList.add(entries.get(i));\n",
+    "            }\n",
+    "        }\n",
+    "        for (SparseArrayEntry e : removeList){\n",
+    "            entries.remove(e);\n",
+    "        }\n",
+    "    }\n",
+    "}\n",
+    "Main.main(null);"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Learnings:\n",
+    "\n",
+    "1. You can't remove an entry in a list while iterating over it like using an enhanced for loop. Instead you can use an iterator.\n",
+    "2. to get the length of an arraylist is use .size()\n",
+    "3. using the size of a list to iterate until is dynamic, so it changes as the list gets bigger. Makes sense because the check is rerun every time."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Java",
+   "language": "java",
+   "name": "java"
+  },
+  "language_info": {
+   "codemirror_mode": "java",
+   "file_extension": ".jshell",
+   "mimetype": "text/x-java-source",
+   "name": "Java",
+   "pygments_lexer": "java",
+   "version": "20.0.2+9"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}