README.md

1881. Maximum Value after Insertion

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 '-'.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn max_value(n: String, x: i32) -> String {
        let x = x as u8 + b'0';
        let mut n = n.into_bytes();

        if n[0] != b'-' {
            for i in 0..=n.len() {
                if i == n.len() || x > n[i] {
                    n.insert(i, x);
                    break;
                }
            }
        } else {
            for i in 1..=n.len() {
                if i == n.len() || x < n[i] {
                    n.insert(i, x);
                    break;
                }
            }
        }

        String::from_utf8(n).unwrap()
    }
}