Function leetcode_for_rust::cd0051_n_queens::_dfs

pub fn _dfs(
    n: i32, 
    result: &mut Vec<Vec<String>>, 
    current_queens: &mut Vec<i32>, 
    row: i32, 
    cols: &mut Vec<i32>, 
    xy_sum: &mut Vec<i32>, 
    xy_sub: &mut Vec<i32>
)