java 386.词典编号（＃1）.java

Posted 2021-05-08

class Solution {
    private void add(List<Integer> res, int m, int n) {
        if (m > n) return;
        if (m != 0) {
            res.add(m);
            for (int i = 0; i <= 9; i++) {
              add(res, m * 10 + i, n);
            }
        } else {
            for (int i = 1; i <= 9; i++) {
              add(res, i, n);
            }
        }
    }
    public List<Integer> lexicalOrder(int n) {
        List<Integer> res = new ArrayList<>();
        if (n == 0) return res;
        add(res, 0, n);
        return res;
    
    }
}

class Solution {
    public List<Integer> lexicalOrder(int n) {
        List<Integer> list = new ArrayList<>(n);
        int curr = 1;
        for (int i = 1; i <= n; i++) {
            list.add(curr);
            if (curr * 10 <= n) {
                curr *= 10;
            } else if (curr % 10 != 9 && curr + 1 <= n) {
                curr++;
            } else {
                while ((curr / 10) % 10 == 9) {
                    curr /= 10;
                }
                curr = curr / 10 + 1;
            }
        }
        return list;
    }
}

public class Solution {
    public List<Integer> lexicalOrder(int n) {
        List<Integer> res = new ArrayList<>();
        for(int i=1;i<10;++i){
          dfs(i, n, res); 
        }
        return res;
    }
    
    public void dfs(int cur, int n, List<Integer> res){
        if(cur>n)
            return;
        else{
            res.add(cur);
            for(int i=0;i<10;++i){
                if(10*cur+i>n)
                    return;
                dfs(10*cur+i, n, res);
            }
        }
    }
}