Rust solutions
One-liner with chain. \n\nimpl Solution {\n    pub fn get_concatenation(nums: Vec<i32>) -> Vec<i32> {\n        nums.iter().chain(nums.iter()).cloned().collect()
1. One-liner with ```chain```. \n```\nimpl Solution {\n    pub fn get_concatenation(nums: Vec<i32>) -> Vec<i32> {\n        nums.iter().chain(nums.iter()).cloned().collect()\n    }\n}\n```\n\n2. One-liner with ```cycle```. \n```\nimpl Solution {\n    pub fn get_concatenation_cycle(nums: Vec<i32>) -> Vec<i32> {\n        nums.iter().cycle().take(nums.len() * 2).cloned().collect()\n    }\n}\n```\n\n3. Element-wise creation of a prepared vector by indices\n```\nimpl Solution {\n    pub fn get_concatenation(nums: Vec<i32>) -> Vec<i32> {\n        let mut res = vec![0; nums.len() * 2];\n        nums.iter().enumerate().for_each(|(ind, &x)| {\n            res[ind] = x;\n            res[ind + nums.len()] = x;\n        });\n        res\n    }\n}\n```
['Rust']