2259. Remove Digit From Number to Maximize Result
Description
You are given a string number
representing a positive integer and a character digit
.
Return the resulting string after removing exactly one occurrence of digit
from number
such that the value of the resulting string in decimal form is maximized. The test cases are generated such that digit
occurs at least once in number
.
Example 1:
Input: number = "123", digit = "3" Output: "12" Explanation: There is only one '3' in "123". After removing '3', the result is "12".
Example 2:
Input: number = "1231", digit = "1" Output: "231" Explanation: We can remove the first '1' to get "231" or remove the second '1' to get "123". Since 231 > 123, we return "231".
Example 3:
Input: number = "551", digit = "5" Output: "51" Explanation: We can remove either the first or second '5' from "551". Both result in the string "51".
Constraints:
2 <= number.length <= 100
number
consists of digits from'1'
to'9'
.digit
is a digit from'1'
to'9'
.digit
occurs at least once innumber
.
Solutions
Solution 1: Brute Force Enumeration
We can enumerate all positions $\textit{i}$ in the string $\textit{number}$. If $\textit{number}[i] = \textit{digit}$, we take the prefix $\textit{number}[0:i]$ and the suffix $\textit{number}[i+1:]$ of $\textit{number}$ and concatenate them. This gives the result after removing $\textit{number}[i]$. We then take the maximum of all possible results.
The time complexity is $O(n^2)$, and the space complexity is $O(n)$. Here, $n$ is the length of the string $\textit{number}$.
1 2 3 4 5 |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 |
|
1 2 3 4 5 6 7 8 9 10 11 12 |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 |
|
Solution 2: Greedy
We can enumerate all positions $\textit{i}$ in the string $\textit{number}$. If $\textit{number}[i] = \textit{digit}$, we record the last occurrence position of $\textit{digit}$ as $\textit{last}$. If $\textit{i} + 1 < \textit{n}$ and $\textit{number}[i] < \textit{number}[i + 1]$, then we can directly return $\textit{number}[0:i] + \textit{number}[i+1:]$ as the result after removing $\textit{number}[i]$. This is because if $\textit{number}[i] < \textit{number}[i + 1]$, removing $\textit{number}[i]$ will result in a larger number.
After the traversal, we return $\textit{number}[0:\textit{last}] + \textit{number}[\textit{last}+1:]$.