Method backtrace

Java/LeetCodeN-Queens.java:20–34

(List<List<String>> result, List<String> list, int level, int n, boolean[] used)

    }
    
     public static void backtrace(List<List<String>> result, List<String> list, int level, int n, boolean[] used){
        if(level == n) result.add(new ArrayList<String>(list));
        else{
            for(int i = 0; i < n; i++){
                if(used[i]) continue;
                if(isValid(list, level, i, n)){
                    list.add(createQueen(n, i));
                    used[i] = true;
                    backtrace(result, list, level + 1, n, used);
                    used[i] = false;
                    list.remove(list.size() - 1);
                }
            }
        }
    }
    public static boolean isValid(List<String> list, int row, int column, int n){
        if(row > 0){
            String cmp = list.get(row - 1);