Problem Description
Given a string n representing a positive decimal integer, determine the minimum number of positive deci-binary numbers needed such that their sum equals n. A deci-binary number is one where each digit is either 0 or 1, with no leading zeros.
Key Insights
- The minimum number of deci-binary numbers required is equal to the maximum digit in the string n.
- Each deci-binary number can contribute at most 1 at each digit position.
- Therefore, for a digit d in n, you need at least d deci-binary numbers to sum up to that particular digit.
Space and Time Complexity
Time Complexity: O(n), where n is the length of the input string, because we iterate through each digit once. Space Complexity: O(1), using a constant amount of extra space.
Solution
The idea behind the solution is based on the observation that for any digit in the number, you must have at least that many deci-binary numbers, since each deci-binary number can only contribute a 1 at that digit's place. Thus, the answer is the maximum digit in the input string n. We simply iterate over the string, convert each character to an integer, and track the maximum value found.