1849. Splitting a String Into Descending Consecutive Values

Problem Link

Description

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You are given a string s that consists of only digits.

Check if we can split s into two or more non-empty substrings such that the numerical values of the substrings are in descending order and the difference between numerical values of every two adjacent substrings is equal to 1.

• For example, the string s = "0090089" can be split into ["0090", "089"] with numerical values [90,89]. The values are in descending order and adjacent values differ by 1, so this way is valid.
• Another example, the string s = "001" can be split into ["0", "01"], ["00", "1"], or ["0", "0", "1"]. However all the ways are invalid because they have numerical values [0,1], [0,1], and [0,0,1] respectively, all of which are not in descending order.

Return true if it is possible to split s​​​​​​ as described above, or false otherwise.

A substring is a contiguous sequence of characters in a string.

 

Example 1:

Input: s = "1234"
Output: false
Explanation: There is no valid way to split s.

Example 2:

Input: s = "050043"
Output: true
Explanation: s can be split into ["05", "004", "3"] with numerical values [5,4,3].
The values are in descending order with adjacent values differing by 1.

Example 3:

Input: s = "9080701"
Output: false
Explanation: There is no valid way to split s.

 

Constraints:

• 1 <= s.length <= 20
• s only consists of digits.

Solution

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Python3

class Solution:
    def splitString(self, s: str) -> bool:
        n = len(s)
        
        def go(i, prev):
            if i == n: return True
            
            valid = False
            
            for j in range(i + 1, n + 1):
                if int(s[i : j]) == prev - 1:
                    valid |= go(j, prev - 1)
                
                if valid: return True
            
            return valid
        
        
        for i in range(1, n):
            if go(i, int(s[:i])):
                return True
        
        return False