## Algorithm

Problem Name: 1253. Reconstruct a 2-Row Binary Matrix

Given the following details of a matrix with `n` columns and `2` rows :

• The matrix is a binary matrix, which means each element in the matrix can be `0` or `1`.
• The sum of elements of the 0-th(upper) row is given as `upper`.
• The sum of elements of the 1-st(lower) row is given as `lower`.
• The sum of elements in the i-th column(0-indexed) is `colsum[i]`, where `colsum` is given as an integer array with length `n`.

Your task is to reconstruct the matrix with `upper`, `lower` and `colsum`.

Return it as a 2-D integer array.

If there are more than one valid solution, any of them will be accepted.

If no valid solution exists, return an empty 2-D array.

Example 1:

```Input: upper = 2, lower = 1, colsum = [1,1,1]
Output: [[1,1,0],[0,0,1]]
Explanation: [[1,0,1],[0,1,0]], and [[0,1,1],[1,0,0]] are also correct answers.
```

Example 2:

```Input: upper = 2, lower = 3, colsum = [2,2,1,1]
Output: []
```

Example 3:

```Input: upper = 5, lower = 5, colsum = [2,1,2,0,1,0,1,2,0,1]
Output: [[1,1,1,0,1,0,0,1,0,0],[1,0,1,0,0,0,1,1,0,1]]
```

Constraints:

• `1 <= colsum.length <= 10^5`
• `0 <= upper, lower <= colsum.length`
• `0 <= colsum[i] <= 2`

## Code Examples

### #1 Code Example with Python Programming

```Code - Python Programming```

``````
class Solution:
def reconstructMatrix(
self, upper: int, lower: int, colsum: List[int]
) -> List[List[int]]:
res = [[0] * len(colsum) for _ in range(2)]
for j, sm in enumerate(colsum):
if sm == 2:
if upper == 0 or lower == 0:
return []
upper -= 1
lower -= 1
res[0][j] = res[1][j] = 1
elif sm:
if upper == lower == 0:
return []
if upper >= lower:
upper -= 1
res[0][j] = 1
else:
lower -= 1
res[1][j] = 1
return res if upper == lower == 0 else []
``````
Copy The Code &

Input

cmd
upper = 2, lower = 1, colsum = [1,1,1]

Output

cmd
[[1,1,0],[0,0,1]]