LeetCode Entry

2022. Convert 1D Array Into 2D Array

01.09.2024 easy 2024 kotlin rust

D to 2D mxn array

2022. Convert 1D Array Into 2D Array easy blog post substack youtube 1.webp

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Problem TLDR

1D to 2D mxn array #easy

Intuition

There are many ways to do this:

  • for y in 0..m for x in 0..n loop
  • for num in original loop
  • using pointer arithmetics in C-like languages (loop unroll and SIMD)
  • using Array constructors in Kotlin
  • using iterators and chunks

Approach

  • pay attention to the description, we also have to check that size is exactly m x n

Complexity

  • Time complexity: \(O(n x m)\)

  • Space complexity: \(O(n x m)\)

Code


    fun construct2DArray(original: IntArray, m: Int, n: Int) =
        if (original.size != n * m) listOf()
        else original.asList().chunked(n)



    pub fn construct2_d_array(original: Vec<i32>, m: i32, n: i32) -> Vec<Vec<i32>> {
        if original.len() as i32 != m * n { vec![] } else
        { original.chunks_exact(n as usize).map(|r| r.to_vec()).collect() }
    }



    vector<vector<int>> construct2DArray(vector<int>& original, int m, int n) {
        if (original.size() != m * n) return {};
        std::vector<std::vector<int>> result; result.reserve(m);
        const int* dataPtr = original.data();
        for (int i = 0; i < m; ++i)
            result.emplace_back(dataPtr + i * n, dataPtr + i * n + n);
        return result;
    }