926. Flip String to Monotone Increasing

Problem Link

Description

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A binary string is monotone increasing if it consists of some number of 0's (possibly none), followed by some number of 1's (also possibly none).

You are given a binary string s. You can flip s[i] changing it from 0 to 1 or from 1 to 0.

Return the minimum number of flips to make s monotone increasing.

 

Example 1:

Input: s = "00110"
Output: 1
Explanation: We flip the last digit to get 00111.

Example 2:

Input: s = "010110"
Output: 2
Explanation: We flip to get 011111, or alternatively 000111.

Example 3:

Input: s = "00011000"
Output: 2
Explanation: We flip to get 00000000.

 

Constraints:

• 1 <= s.length <= 105
• s[i] is either '0' or '1'.

Solution

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Python3

class Solution:
    def minFlipsMonoIncr(self, s: str) -> int:
        flipCount = oneCount = 0
 
        for x in s:
            if x == '0':
                flipCount += 1
            else:
                oneCount += 1
            
            flipCount = min(flipCount, oneCount)
 
        return flipCount