1864

class Solution {
public:
    int minSwaps(string s) {
        int oddOnes = 0, evenOnes = 0, countOnes = 0;
        for(int i=0; i<s.length(); i++){
            int ch = s[i]-'0';
            if(ch == 0) countOnes++;
            if(i&1 && !ch) oddOnes++;
            if(i%2 == 0 && !ch) evenOnes++;
        }
        int n = s.length();
        if(n&1){
            if(countOnes == n/2){
                return (n/2)-oddOnes;
            }
            else if(countOnes == (n/2)+1){
                return (n/2)+1-evenOnes;
            }
        }
        else{
            if(countOnes == n/2)
                return ((n/2)-max(oddOnes, evenOnes));
        }
        return -1;
    }
};