1291. 顺次数

怎么说呢，这种题已经挡不住我了????

 

import java.util.LinkedList;
import java.util.List;

class Solution {

    List<Integer> res = new LinkedList<>();

    private void dfs(String s, int len, boolean sign[], int low, int high, int index){


        if(s.length() == len){
            int a = Integer.valueOf(s);
            if(a <= high && a >= low){
                res.add(Integer.valueOf(s));
            }
            return;
        }

        for(int j = index; j < 10; j++){
            if(sign[j]){
                continue;
            }

            if(s.length() == 0){
                s += (""+j);
                sign[j] = true;
                dfs(s, len, sign, low, high, j);
                sign[j] = false;
                s = s.substring(0, s.length()-1);
            }else if(Integer.valueOf(""+s.charAt(s.length()-1)) == j-1){
                s += (""+j);
                sign[j] = true;
                dfs(s, len, sign, low, high, j);
                sign[j] = false;
                s = s.substring(0, s.length()-1);
            }

        }
    }

    public List<Integer> sequentialDigits(int low, int high) {

        int len_low = String.valueOf(low).length();
        int len_high = String.valueOf(high).length();

        boolean sign[] = new boolean[10];

        for(int i=len_low; i<=len_high; i++){
            dfs("", i, sign, low, high, 1);
        }

        for(int a: res){
            System.out.println(a);
        }
        return res;
    }

    public static void main(String[] args) {
        Solution s = new Solution();
        s.sequentialDigits(100, 300);
    }
}