LeetCode-in-Java

2522. Partition String Into Substrings With Values at Most K

Medium

You are given a string s consisting of digits from 1 to 9 and an integer k.

A partition of a string s is called good if:

• Each digit of s is part of exactly one substring.
• The value of each substring is less than or equal to k.

Return the minimum number of substrings in a good partition of s. If no good partition of s exists, return -1.

Note that:

• The value of a string is its result when interpreted as an integer. For example, the value of "123" is 123 and the value of "1" is 1.
• A substring is a contiguous sequence of characters within a string.

Example 1:

Input: s = “165462”, k = 60

Output: 4

Explanation: We can partition the string into substrings “16”, “54”, “6”, and “2”. Each substring has a value less than or equal to k = 60. It can be shown that we cannot partition the string into less than 4 substrings.

Example 2:

Input: s = “238182”, k = 5

Output: -1

Explanation: There is no good partition for this string.

Constraints:

• 1 <= s.length <= 105
• s[i] is a digit from '1' to '9'.
• 1 <= k <= 109

Solution

public class Solution {
    public int minimumPartition(String s, int k) {
        if (k == 9) {
            return s.length();
        }
        int partitions = 1;
        long partitionValue = 0;
        long digit;
        for (int i = 0; i < s.length(); i++) {
            digit = (long) s.charAt(i) - '0';
            if (digit > k) {
                return -1;
            }
            partitionValue = partitionValue * 10 + digit;
            if (partitionValue > k) {
                partitionValue = digit;
                partitions++;
            }
        }
        return partitions;
    }
}

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