LeetCode: Remove 9

Posted on May 7, 2018July 26, 2020 by braindenny

Remove 9

Similar Problems:

Start from integer 1, remove any integer that contains 9 such as 9, 19, 29…

So now, you will have a new integer sequence: 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, …

Given a positive integer n, you need to return the n-th integer after removing. Note that 1 will be the first integer.

Example 1:
Input: 9
Output: 10

Hint: n will not exceed 9 x 10^8.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

Solution: without array

// https://code.dennyzhang.com/remove-9
// Basic Ideas: base conversion
//
//  Convert n to base 9
//
// Complexity: Time O(log(n)), Space O(1)
func newInteger(n int) int {
    res, base := 0, 1
    for n != 0 {
        res = res+n%9*base
        n = n/9
        base *= 10
    }
    return res
}

Solution: with array

// https://code.dennyzhang.com/remove-9
// Basic Ideas: base conversion
//
//  Convert n to base 9
//
// Complexity: Time O(1), Space O(1)
func newInteger(n int) int {
    nums := []int{}
    for n != 0 {
        nums = append(nums, n%9)
        n = n/9
    }
    res := 0
    for i:=len(nums)-1; i>=0; i-- {
        res = res*10+nums[i]
    }
    return res
}

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