Method solveNQueens

Java/LeetCodeN-Queens.java:13–18

(int n)

class Solution {
    public List<List<String>> solveNQueens(int n) {
        List<List<String>> results = new ArrayList<>();
        if(n ==0) return results;
        backtrace(results, new ArrayList<String>(), 0, n, new boolean[n]);
        return results;
    }
    
     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));