README_EN.md

1881. Maximum Value after Insertion

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Description

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

Python3

class Solution:
    def maxValue(self, n: str, x: int) -> str:
        negative = n[0] == '-'
        i, res = 0, []
        if negative:
            i += 1
            res.append('-')
        find = False
        while i < len(n):
            num = int(n[i])
            if (negative and x < num) or (not negative and x > num):
                res.append(str(x))
                find = True
                break
            res.append(n[i])
            i += 1
        res.append(n[i:] if find else str(x))
        return ''.join(res)

Java

class Solution {
    public String maxValue(String n, int x) {
        boolean negative = n.charAt(0) == '-';
        StringBuilder res = new StringBuilder();
        int i = 0;
        if (negative) {
            ++i;
            res.append("-");
        }
        boolean find = false;
        for (; i < n.length(); ++i) {
            int num = n.charAt(i) - '0';
            if ((negative && x < num) || (!negative && x > num)) {
                res.append(x);
                find = true;
                break;
            }
            res.append(n.charAt(i));
        }
        res.append(find ? n.substring(i) : x);
        return res.toString();
    }
}

JavaScript

/**
 * @param {string} n
 * @param {number} x
 * @return {string}
 */
 var maxValue = function(n, x) {
    let nums = [...n];
    let sign = 1, i = 0;
    if (nums[0] == '-') {
        sign = -1;
        i++;
    }
    while (i < n.length && (nums[i] - x) * sign >= 0) {
        i++;
    }
    nums.splice(i, 0, x);
    return nums.join('');
};

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