## 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`

## Rust Solution

``````struct Solution;

impl Solution {
fn reconstruct_matrix(mut upper: i32, mut lower: i32, colsum: Vec<i32>) -> Vec<Vec<i32>> {
let n = colsum.len();
let mut res = vec![vec![0; n]; 2];
for j in 0..n {
match colsum[j] {
2 => {
res[0][j] = 1;
res[1][j] = 1;
upper -= 1;
lower -= 1;
}
1 => {
if upper >= lower {
res[0][j] = 1;
upper -= 1;
} else {
res[1][j] = 1;
lower -= 1;
}
}
_ => {}
}
}
if upper == 0 && lower == 0 {
res
} else {
vec![]
}
}
}

#[test]
fn test() {
let upper = 2;
let lower = 1;
let colsum = vec![1, 1, 1];
let res = vec_vec_i32![[1, 1, 0], [0, 0, 1]];
assert_eq!(Solution::reconstruct_matrix(upper, lower, colsum), res);
let upper = 2;
let lower = 3;
let colsum = vec![2, 2, 1, 1];
let res = vec_vec_i32![];
assert_eq!(Solution::reconstruct_matrix(upper, lower, colsum), res);
let upper = 5;
let lower = 5;
let colsum = vec![2, 1, 2, 0, 1, 0, 1, 2, 0, 1];
let res = vec_vec_i32![
[1, 1, 1, 0, 0, 0, 1, 1, 0, 0],
[1, 0, 1, 0, 1, 0, 0, 1, 0, 1]
];
assert_eq!(Solution::reconstruct_matrix(upper, lower, colsum), res);
}
``````

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