Given an integer array nums
of length n
, you want to create an array ans
of length 2n
where ans[i] == nums[i]
and ans[i + n] == nums[i]
for 0 <= i < n
(0-indexed).
Specifically, ans
is the concatenation of two nums
arrays.
Return the array ans
.
Example 1:
Input: nums = [1,2,1] Output: [1,2,1,1,2,1] Explanation: The array ans is formed as follows: - ans = [nums[0],nums[1],nums[2],nums[0],nums[1],nums[2]] - ans = [1,2,1,1,2,1]
Example 2:
Input: nums = [1,3,2,1] Output: [1,3,2,1,1,3,2,1] Explanation: The array ans is formed as follows: - ans = [nums[0],nums[1],nums[2],nums[3],nums[0],nums[1],nums[2],nums[3]] - ans = [1,3,2,1,1,3,2,1]
Constraints:
n == nums.length
1 <= n <= 1000
1 <= nums[i] <= 1000
Solution: Pre-allocation
Pre-allocate an array of length 2 * n.
ans[i] = nums[i % n]
Time complexity: O(n)
Space complexity: O(n)
C++
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// Author: Huahua class Solution { public: vector<int> getConcatenation(vector<int>& nums) { const int n = nums.size(); vector<int> ans(2 * n); for (int i = 0; i < 2 * n; ++i) ans[i] = nums[i % n]; return ans; } }; |
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