1291. Sequential Digits

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題目敘述

An integer has sequential digits if and only if each digit in the number is one more than the previous digit.

Return a sorted list of all the integers in the range [low, high] inclusive that have sequential digits.

Example 1

Input: low = 100, high = 300 Output: [123,234]

Example 2

Input: low = 1000, high = 13000 Output: [1234,2345,3456,4567,5678,6789,12345]

解題思路

Solution

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

class Solution {
    public List<Integer> sequentialDigits(int low, int high) {
        List<Integer> ans = new ArrayList<>();

        for(int i = 1; i <= 9; i++){
            int num = i;
            int next = i + 1;

            while (num <= high && next <= 9) {
                num = num * 10 + next;
                next = next + 1;
                if(num >= low && num <= high){
                    ans.add(num);
                }
            }
        }
        
        Collections.sort(ans);

        return ans;
    }
}