Lexicographical Numbers Problem


Description

LeetCode Problem 386.

Given an integer n, return all the numbers in the range [1, n] sorted in lexicographical order. You must write an algorithm that runs inO(n)time and uses O(1) extra space.

Example 1:

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Input: n = 13
Output: [1,10,11,12,13,2,3,4,5,6,7,8,9]

Example 2:

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Input: n = 2
Output: [1,2]

Constraints:

  • 1 <= n <= 5 * 10^4


Sample C++ Code

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class Solution {
public:
    vector<int> lexicalOrder(int n) {
        vector<int> res(n);
        int cur = 1;
        for (int i = 0; i < n; i++) {
            res[i] = cur;
            if (cur * 10 <= n) {
                cur *= 10;
            } else {
                if (cur >= n) 
                    cur /= 10;
                cur += 1;
                while (cur % 10 == 0)
                    cur /= 10;
            }
        }
        return res;
    }
};




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