Leetcode 2022 Convert 1-D array to 2-D array
Problem Statement — You are given a 0-indexed 1-dimensional (1D) integer array original
, and two integers, m
and n
. You are tasked with creating a 2-dimensional (2D) array with m
rows and n
columns using all the elements from original
.
The elements from indices 0
to n - 1
(inclusive) of original
should form the first row of the constructed 2D array, the elements from indices n
to 2 * n - 1
(inclusive) should form the second row of the constructed 2D array, and so on.
Return an m x n
2D array constructed according to the above procedure, or an empty 2D array if it is impossible.
Example 1:
Input: original = [1,2,3,4], m = 2, n = 2
Output: [[1,2],[3,4]]
Explanation: The constructed 2D array should contain 2 rows and 2 columns.
The first group of n=2 elements in original, [1,2], becomes the first row in the constructed 2D array.
The second group of n=2 elements in original, [3,4], becomes the second row in the constructed 2D array.
Example 2:
Input: original = [1,2,3], m = 1, n = 3
Output: [[1,2,3]]
Explanation: The constructed 2D array should contain 1 row and 3 columns.
Put all three elements in original into the first row of the constructed 2D array.
Example 3:
Input: original = [1,2], m = 1, n = 1
Output: []
Explanation: There are 2 elements in original.
It is impossible to fit 2 elements in a 1x1 2D array, so return an empty 2D array.
Constraints:
1 <= original.length <= 5 * 104
1 <= original[i] <= 105
1 <= m, n <= 4 * 104
Time: O(m * n)
Space : O(m * n)
class Solution {
public:
vector<vector<int>> construct2DArray(vector<int>& original, int m, int n) {
if (original.size() != m*n)
return {};
vector<vector<int>> ans(m, vector<int>(n,0));
int k = 0;
for (int i = 0; i < m; ++i) {
for (int j = 0; j < n; ++j) {
ans[i][j] = original[k++];
}
}
return ans;
}
};
Time: O(m * n)
Space : O(m * n)
class Solution {
public:
vector<vector<int>> construct2DArray(vector<int>& original, int m, int n) {
if (original.size() != m*n)
return {};
vector<vector<int>> ans(m, vector<int>(n,0));
for(int i=0;i<original.size();i++)
ans[i/n][i%n] = original[i];
return ans;
}
};
Feel free to ask any question in the comment section.
I hope that you’ve found the solution useful.