✅Detailed Explanation💯5 Different Ways to Solve in Python🔥Beginner Friendly🔥
\n\n\n 5 Methods Code Summary (Click to Expand)\n\npython []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        result = [
\n\n<details>\n<summary><h2> 5 Methods Code Summary (Click to Expand)</h2></summary>\n\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        result = []\n        for num in nums:\n            result.append(num)  # Add each element from nums\n        for num in nums:\n            result.append(num)  # Add each element again\n        return result\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        n = len(nums)\n        result = [0] * (2 * n)  # Create a new list of size 2n\n        for i in range(n):\n            result[i] = nums[i]      # Copy the first part\n            result[i + n] = nums[i]  # Copy the second part\n        return result\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        nums.extend(nums)  # Extend the list with itself\n        return nums\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        return nums + nums  # Concatenate the list with itself\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        return nums * 2  # Repeat the list twice\n```\n\n</details>\n\n---\n\n# \uD83C\uDFAF Problem Explanation:\nWe are given a `array` or in python we call it a `list`.\nThe goal is to concatenate/combine/add the list with itself, meaning if the input array is `[1, 2, 3]`, the output should be `[1, 2, 3, 1, 2, 3]`.\n\n## \uD83D\uDD0D Methods To Solve This Problem:\nThis post covers five different methods to concatenate an array with itself in Python. Each method is explained in a beginner-friendly way.\n1. Using Loop and Append Method\n2. Using Loop and Changing Element Value\n3. Using Extend Method\n4. Using `+` Operator\n5. Using `*` Operator\n\n\n\n---\n\n# Method 1: Using Loop and Append Method\n\nIn this method, we use a loop to add each element from the original list to a new list twice.\n\n### \uD83E\uDDE0 Approach:\n1. Start with an empty list called `result`.\n2. Loop through the original list and append each element to `result`.\n3. Loop through the original list again and append each element to `result`.\n4. Return the `result` list.\n\n### \uD83E\uDDD1\u200D\uD83D\uDCBB Code\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        result = []\n        for num in nums:\n            result.append(num)  # Add each element from nums\n        for num in nums:\n            result.append(num)  # Add each element again\n        return result\n```\n\n---\n\n# Method 2: Using Loop and Changing Element Value\n\nIn this method, we create a new list of the required size and use a loop to set each element.\n\n### \uD83E\uDDE0 Approach:\n1. Determine the length of the original list.\n2. Create a new list called `result` with twice the length of the original list.\n3. Use a loop to set each element in the new list:\n   - First, copy elements from the original list.\n   - Then, copy elements from the original list again, starting at the next index.\n4. Return the `result` list.\n\n### \uD83E\uDDD1\u200D\uD83D\uDCBB Code\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        n = len(nums)\n        result = [0] * (2 * n)  # Create a new list of size 2n\n        for i in range(n):\n            result[i] = nums[i]      # Copy the first part\n            result[i + n] = nums[i]  # Copy the second part\n        return result\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        n = len(nums)\n        result = [0] * (2 * n)  # Create a new list of size 2n\n        for i, num in enumerate(nums):\n            result[i] = num         # Copy the first part\n            result[i + n] = num     # Copy the second part\n        return result\n```\n\n> Above two methods are very beginner way to do. Next 3 are way easier and faster.\n\n---\n\n# Method 3: Using Extend Method\n\nIn this method, we use the `extend` method to add elements from the original list to itself.\n\n### \uD83E\uDDE0 Approach:\n1. Use the `extend` method to add elements from the original list to itself.\n2. Return the modified list.\n\n### \uD83E\uDDD1\u200D\uD83D\uDCBB Code\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        nums.extend(nums)  # Extend the list with itself\n        return nums\n```\n\n---\n\n# Method 4: Using `+` Operator\n\nIn this method, we use the `+` operator to concatenate the list with itself.\n\n### \uD83E\uDDE0 Approach:\n1. Use the `+` operator to concatenate the list with itself.\n2. Return the new list.\n\n### \uD83E\uDDD1\u200D\uD83D\uDCBB Code\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        return nums + nums  # Concatenate the list with itself\n```\n\n---\n\n# Method 5: Using `*` Operator\n\nIn this method, we use the `*` operator to create a new list with the original list repeated twice.\n\n### \uD83E\uDDE0 Approach:\n1. Use the `*` operator to repeat the list twice.\n2. Return the new list.\n\n### \uD83E\uDDD1\u200D\uD83D\uDCBB Code\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        return nums * 2  # Repeat the list twice\n```\n\n## \uD83D\uDCD2 Complexity:\n- \u23F0 Time complexity: $$O(n)$$. In all the methods, we iterate through the list nums once, performing constant-time operations for each element.\n- \uD83E\uDDFA Space complexity: $$O(n)$$, as they require additional space proportional to the size of the input list to hold the concatenated result.\n\n---\n\n\n# 5 Methods in one place\n\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        result = []\n        for num in nums:\n            result.append(num)  # Add each element from nums\n        for num in nums:\n            result.append(num)  # Add each element again\n        return result\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        n = len(nums)\n        result = [0] * (2 * n)  # Create a new list of size 2n\n        for i in range(n):\n            result[i] = nums[i]      # Copy the first part\n            result[i + n] = nums[i]  # Copy the second part\n        return result\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        nums.extend(nums)  # Extend the list with itself\n        return nums\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        return nums + nums  # Concatenate the list with itself\n```\n``` python []\nclass Solution:\n    def getConcatenation(self, nums: List[int]) -> List[int]:\n        return nums * 2  # Repeat the list twice\n```\n\n---\n# Please consider giving an Upvote!\n![upvote.png](https://assets.leetcode.com/users/images/5fbeecf2-18f6-4dce-a4a0-f11c859e46ad_1714711173.2665718.png)\n
['Array', 'Python', 'Python3']