926. Flip String to Monotone Increasing

Medium (Trung bình) Python 🔗 Xem trên LeetCode

📋 Đề Bài

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'.

💻 Lời Giải

Python 0926-flip-string-to-monotone-increasing.py 
class Solution:
    def minFlipsMonoIncr(self, s: str) -> int:
        n = len(s)
        pref, suff = 0, s.count('0')
        ans = n
        
        for c in s:
            suff -= c == '0'
            ans = min(ans, pref + suff)
            pref += c == '1'
            
        return ans