fn is_min(mat: &[Vec<u64>], col: usize, row: usize) -> bool {
    (0..mat.len()).all(|r| mat[r][col] >= mat[row][col])
}

pub fn find_saddle_points(input: &[Vec<u64>]) -> Vec<(usize, usize)> {
    let mut res = vec![];
    for (row,relem) in input.iter().enumerate() {
        let m = relem.iter().max();
        for (col,celem) in relem.iter().enumerate() {
            if (m == Some(celem)) && is_min(input,col,row) {
                res.push((row,col));
            }
        }
    }
    res
}