LeetCode in Kotlin

1881. Maximum Value after Insertion

Medium

You are given a very large integer n, represented as a string, and an integer digit x. The digits in n and the digit x are in the inclusive range [1, 9], and n may represent a negative number.

You want to maximize n’s numerical value by inserting x anywhere in the decimal representation of n. You cannot insert x to the left of the negative sign.

• For example, if n = 73 and x = 6, it would be best to insert it between 7 and 3, making n = 763.
• If n = -55 and x = 2, it would be best to insert it before the first 5, making n = -255.

Return a string representing the maximum value of n_ after the insertion_.

Example 1:

Input: n = “99”, x = 9

Output: “999”

Explanation: The result is the same regardless of where you insert 9.

Example 2:

Input: n = “-13”, x = 2

Output: “-123”

Explanation: You can make n one of {-213, -123, -132}, and the largest of those three is -123.

Constraints:

• 1 <= n.length <= 105
• 1 <= x <= 9
• The digits in n are in the range [1, 9].
• n is a valid representation of an integer.
• In the case of a negative n, it will begin with '-'.

Solution

class Solution {
    fun maxValue(n: String, x: Int): String {
        var i = 0
        val sign = if (n[0] == '-') -1 else 1
        while (i < n.length) {
            if (n[i] != '-' && sign * (n[i].code - '0'.code) < sign * x) {
                break
            }
            i++
        }
        return n.substring(0, i) + x + n.substring(i)
    }
}

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