added stack problem

serverx-org · Oct 11, 2024 · 2d9c198 · 2d9c198
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diff --git a/Python/02 - Data_Structures/01 - Arrays/Medium/Remove_duplicates.ipynb b/Python/02 - Data_Structures/01 - Arrays/Medium/Remove_duplicates.ipynb
@@ -0,0 +1,81 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Problem: Remove Duplicates from Array\n",
+    "\n",
+    "- **Problem**: Given an array, write a function to remove duplicates without using extra space.\n",
+    "- **Example**:\n",
+    "  ```python\n",
+    "  arr = [1, 2, 2, 3, 4, 4, 5]\n",
+    "  # Output: [1, 2, 3, 4, 5]\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[1, 2, 3, 4, 5]\n"
+     ]
+    }
+   ],
+   "source": [
+    "def remove_duplicates(arr):\n",
+    "    if len(arr) == 0:\n",
+    "        return []\n",
+    "    \n",
+    "    # Pointer for the position of the unique element\n",
+    "    unique_index = 0\n",
+    "\n",
+    "    # Iterate through the array, starting from the second element\n",
+    "    for i in range(1, len(arr)):\n",
+    "        # If the current element is not equal to the element at unique_index\n",
+    "        if arr[i] != arr[unique_index]:\n",
+    "            unique_index += 1  # Move the unique_index\n",
+    "            arr[unique_index] = arr[i]  # Place the non-duplicate element at unique_index\n",
+    "    \n",
+    "    # Return the portion of the array with unique elements\n",
+    "    return arr[:unique_index + 1]\n",
+    "\n",
+    "# Example\n",
+    "arr = [1, 2, 2, 3, 4, 4, 5]\n",
+    "print(remove_duplicates(arr))  # Output: [1, 2, 3, 4, 5]\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "base",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.12.5"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}
diff --git a/Python/02 - Data_Structures/02 - Stack/Easy/Stack_operations.ipynb b/Python/02 - Data_Structures/02 - Stack/Easy/Stack_operations.ipynb
@@ -0,0 +1,100 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Problem: Basic Stack Operations\n",
+    "\n",
+    "- **Problem**: Implement a stack with basic operations such as `push`, `pop`, `peek`, and `is_empty`. Stacks follow a Last In, First Out (LIFO) structure.\n",
+    "- **Example**:\n",
+    "  ```python\n",
+    "  stack = Stack()\n",
+    "  stack.push(10)  # Stack: [10]\n",
+    "  stack.push(20)  # Stack: [10, 20]\n",
+    "  print(stack.pop())  # Output: 20, Stack: [10]\n",
+    "  print(stack.peek())  # Output: 10, Stack: [10]\n",
+    "  print(stack.is_empty())  # Output: False\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "20\n",
+      "10\n",
+      "False\n",
+      "[10]\n"
+     ]
+    }
+   ],
+   "source": [
+    "class Stack:\n",
+    "    def __init__(self):\n",
+    "        # Initialize an empty list to hold stack elements\n",
+    "        self.stack = []\n",
+    "    \n",
+    "    def push(self, value):\n",
+    "        \"\"\"Push an element onto the stack.\"\"\"\n",
+    "        self.stack.append(value)\n",
+    "    \n",
+    "    def pop(self):\n",
+    "        \"\"\"Remove and return the top element of the stack.\"\"\"\n",
+    "        if not self.is_empty():\n",
+    "            return self.stack.pop()\n",
+    "        else:\n",
+    "            return \"Stack is empty\"\n",
+    "    \n",
+    "    def peek(self):\n",
+    "        \"\"\"Return the top element without removing it.\"\"\"\n",
+    "        if not self.is_empty():\n",
+    "            return self.stack[-1]\n",
+    "        else:\n",
+    "            return \"Stack is empty\"\n",
+    "    \n",
+    "    def is_empty(self):\n",
+    "        \"\"\"Check if the stack is empty.\"\"\"\n",
+    "        return len(self.stack) == 0\n",
+    "    \n",
+    "    def display(self):\n",
+    "        \"\"\"Display the stack.\"\"\"\n",
+    "        return self.stack\n",
+    "\n",
+    "# Example\n",
+    "stack = Stack()\n",
+    "stack.push(10)  # Stack: [10]\n",
+    "stack.push(20)  # Stack: [10, 20]\n",
+    "print(stack.pop())  # Output: 20, Stack: [10]\n",
+    "print(stack.peek())  # Output: 10, Stack: [10]\n",
+    "print(stack.is_empty())  # Output: False\n",
+    "print(stack.display())  # Output: [10]\n"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "base",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.12.5"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}
diff --git a/Python/02 - Data_Structures/02 - Stack/Medium/Reverse_string_using_stack.ipynb b/Python/02 - Data_Structures/02 - Stack/Medium/Reverse_string_using_stack.ipynb
@@ -0,0 +1,75 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Problem: Reverse a String Using Stack\n",
+    "\n",
+    "- **Problem**: Given a string, write a function to reverse the string using a stack.\n",
+    "  \n",
+    "- **Example**:\n",
+    "  ```python\n",
+    "  input_str = \"hello\"\n",
+    "  # Output: \"olleh\"\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "olleh\n"
+     ]
+    }
+   ],
+   "source": [
+    "def reverse_string(s):\n",
+    "    # Initialize an empty stack\n",
+    "    stack = []\n",
+    "    \n",
+    "    # Push each character of the string onto the stack\n",
+    "    for char in s:\n",
+    "        stack.append(char)\n",
+    "    \n",
+    "    # Initialize an empty result string\n",
+    "    reversed_str = ''\n",
+    "    \n",
+    "    # Pop characters from the stack and append them to the result string\n",
+    "    while stack:\n",
+    "        reversed_str += stack.pop()\n",
+    "    \n",
+    "    return reversed_str\n",
+    "\n",
+    "# Example\n",
+    "input_str = \"hello\"\n",
+    "print(reverse_string(input_str))  # Output: \"olleh\"\n"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "base",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.12.5"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}