Flip String to Monotone Increasing

Problem Statement - link #

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.

Examples #

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 <= 10^5
• s[i] is either '0' or '1'

Solutions #

class Solution {
public:
    int minFlipsMonoIncr(string s) {
        int flipCount = 0;
        int oneCount = 0;
        for(auto c: s){
            if(c=='1') oneCount++;
            else {
                flipCount++;
                flipCount = min(flipCount, oneCount);
            }
        }
        return flipCount;

    }
};