DSA LAB practice STACKs.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Postfix "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "The prefix exp of infix exp A + B * C - D / E * H is \n",
      " AB+CD-*EH*/\n"
     ]
    }
   ],
   "source": [
    "class Stack:\n",
    "    def __init__(self):\n",
    "        self.items = []\n",
    "    def isEmpty(self):\n",
    "        return self.items == []\n",
    "    def push(self,item):\n",
    "        self.items.append(item)\n",
    "    def pop(self):\n",
    "        return self.items.pop()\n",
    "    def peek(self):\n",
    "        return self.items[len(self.items)-1]\n",
    "    def size(self):\n",
    "        return len(self.items)\n",
    "\n",
    "def infix_postfix(infixexp):\n",
    "    prec = {}\n",
    "    prec[\"^\"] = 4\n",
    "    prec[\"*\"] = 3\n",
    "    prec[\"/\"] = 3\n",
    "    prec[\"+\"] = 2\n",
    "    prec[\"-\"] = 2\n",
    "    prec[\"(\"] = 1\n",
    "\n",
    "    opStack = Stack()\n",
    "    postfixList = []\n",
    "    tokenList = infixexp.split()\n",
    "    for token in tokenList:\n",
    "        if token in \"ABCDEFGHIJKLMNOPQRSTUVWXYZ\" or token in \"abcdefghijklmnopqrstuvwxyz\" or token in \"0123456789\":\n",
    "            postfixList.append(token)\n",
    "        elif token == '(':\n",
    "            opStack.push(token)\n",
    "        elif token == ')':\n",
    "            topToken = opStack.pop()\n",
    "            while topToken != '(':\n",
    "                postfixList.append(topToken)\n",
    "                topToken = opStack.pop()\n",
    "        else:\n",
    "            while (not opStack.isEmpty()) and (prec[opStack.peek()]>=prec[token]):\n",
    "                postfixList.append(opStack.pop())\n",
    "            opStack.push(token)\n",
    "    while not opStack.isEmpty():\n",
    "        postfixList.append(opStack.pop())\n",
    "    return \"\".join(postfixList)\n",
    "        \n",
    "a = infix_postfix('( A + B ) * ( C - D ) / ( E * H )')\n",
    "print(\"The prefix exp of infix exp A + B * C - D / E * H is \\n\",a)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Prefix "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['H']\n",
      "['H']\n",
      "['H', 'E']\n",
      "['H', 'E', '*']\n",
      "['H', 'E', '*', 'D']\n",
      "['H', 'E', '*', 'D', '/']\n",
      "['H', 'E', '*', 'D', '/', 'C']\n",
      "['H', 'E', '*', 'D', '/', 'C']\n",
      "['H', 'E', '*', 'D', '/', 'C', 'B']\n",
      "['H', 'E', '*', 'D', '/', 'C', 'B', '*', '-']\n",
      "['H', 'E', '*', 'D', '/', 'C', 'B', '*', '-', 'A']\n",
      "The prefix exp of infix exp A + B * C - D / E * H is \n",
      " +A-*BC/D*EH\n"
     ]
    }
   ],
   "source": [
    "class Stack:\n",
    "    def __init__(self):\n",
    "        self.items = []\n",
    "    def isEmpty(self):\n",
    "        return self.items == []\n",
    "    def push(self,item):\n",
    "        self.items.append(item)\n",
    "    def pop(self):\n",
    "        return self.items.pop()\n",
    "    def peek(self):\n",
    "        return self.items[len(self.items)-1]\n",
    "    def size(self):\n",
    "        return len(self.items)\n",
    "\n",
    "def infix_prefix(infixexp):\n",
    "    prec = {}\n",
    "    prec[\"^\"] = 4\n",
    "    prec[\"*\"] = 3\n",
    "    prec[\"/\"] = 3\n",
    "    prec[\"+\"] = 2\n",
    "    prec[\"-\"] = 2\n",
    "    prec[\"(\"] = 1\n",
    "\n",
    "    opStack = Stack()\n",
    "    postfixList = []\n",
    "    tokenList = infixexp.split(' ')\n",
    "    for token in tokenList[::-1]:\n",
    "        \n",
    "        if token in \"ABCDEFGHIJKLMNOPQRSTUVWXYZ\" or token in \"abcdefghijklmnopqrstuvwxyz\" or token in \"0123456789\":\n",
    "            postfixList.append(token)\n",
    "        elif token == '(':\n",
    "            opStack.push(token)\n",
    "        elif token == ')':\n",
    "            topToken = opStack.pop()\n",
    "            while topToken != '(':\n",
    "                postfixList.append(topToken)\n",
    "                topToken = opStack.pop()\n",
    "        else:\n",
    "            while (not opStack.isEmpty()) and (prec[opStack.peek()]>=prec[token]):\n",
    "                postfixList.append(opStack.pop())\n",
    "            opStack.push(token)\n",
    "        print([a for a in postfixList])\n",
    "    while not opStack.isEmpty():\n",
    "        postfixList.append(opStack.pop())\n",
    "    z  =  []\n",
    "    for a in postfixList[::-1]:\n",
    "        z.append(a)\n",
    "    postfixList = z\n",
    "    return \"\".join(postfixList)\n",
    "        \n",
    "a = infix_prefix('A + B * C - D / E * H')\n",
    "print(\"The prefix exp of infix exp A + B * C - D / E * H is \\n\",a)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "False ^ False"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "The prefix exp of infix exp A + B * C - D / E * H is \n",
      " +A-*BC/D*EH\n"
     ]
    }
   ],
   "source": [
    "class Stack:\n",
    "    def __init__(self):\n",
    "        self.items = []\n",
    "    def isEmpty(self):\n",
    "        return self.items == []\n",
    "    def push(self,item):\n",
    "        self.items.append(item)\n",
    "    def pop(self):\n",
    "        return self.items.pop()\n",
    "    def peek(self):\n",
    "        return self.items[len(self.items)-1]\n",
    "    def size(self):\n",
    "        return len(self.items)\n",
    "\n",
    "def infix_prefix(infixexp):\n",
    "    prec = {}\n",
    "    prec[\"^\"] = 4\n",
    "    prec[\"*\"] = 3\n",
    "    prec[\"/\"] = 3\n",
    "    prec[\"+\"] = 2\n",
    "    prec[\"-\"] = 2\n",
    "    prec[\"(\"] = 1\n",
    "\n",
    "    opStack = Stack()\n",
    "    postfixList = []\n",
    "    tokenList = infixexp.split(' ')\n",
    "    for token in tokenList[::-1]:\n",
    "        \n",
    "        if token in \"ABCDEFGHIJKLMNOPQRSTUVWXYZ\" or token in \"abcdefghijklmnopqrstuvwxyz\" or token in \"0123456789\":\n",
    "            postfixList.append(token)\n",
    "        elif token == '(':\n",
    "            opStack.push(token)\n",
    "        elif token == ')':\n",
    "            topToken = opStack.pop()\n",
    "            while topToken != '(':\n",
    "                postfixList.append(topToken)\n",
    "                topToken = opStack.pop()\n",
    "        else:\n",
    "            while (not opStack.isEmpty()) and (prec[opStack.peek()]>=prec[token]):\n",
    "                postfixList.append(opStack.pop())\n",
    "            opStack.push(token)\n",
    "    while not opStack.isEmpty():\n",
    "        postfixList.append(opStack.pop())\n",
    "    z  =  []\n",
    "    for a in postfixList[::-1]:\n",
    "        z.append(a)\n",
    "    postfixList = z\n",
    "    return \"\".join(postfixList)\n",
    "        \n",
    "a = infix_prefix('A + B * C - D / E * H')\n",
    "print(\"The prefix exp of infix exp A + B * C - D / E * H is \\n\",a)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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