Partition String Into Substrings With Values at Most K

Problem Statement - link #

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.

Examples #

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 <= 10^5
• s[i] is a digit from ‘1’ to ‘9’
• 1 <= k <= 10^9

Solutions #

class Solution {
public:
    int minimumPartition(string s, int k) {
        long long cur = 0, res = 0;
        for(int i = 0; i < s.length(); i++) {
            cur = cur * 10 + (s[i] - '0');
            if(cur > k) {
                res++;
                cur = s[i] - '0';
            }
            if(cur > k) {
                return -1;
            }
        }
        return res + 1;

    }
};