Leetcode #1529: Bulb Switcher IV (https://www.InterviewRecipes.com/leetcode-1529)

Leetcode_1529.cpp

class Solution {
   inline char toggle(char c) {
     return c == '0' ?  '1' : '0';
   }
public:
    int minFlips(string target) {
        int n = target.size();           // Total bulbs.
        int flips = 0;                   // Final answer.
        char status = '0';               // This stores the status of bulbs that
                                         // are ahead of current index `i`.
        for (int i=0; i<n; i++) {        // For each bulb -
            if (status != target[i]) {   // If what we want is different from what
                                         // it is at this moment, make a flip.
                flips++;                 // We made a flip.
                status = toggle(status); // Now status of remaining
                                         // bulbs have changed.
            }
        }
        return flips;                    // Awesome, return the answer now.
    }
};