Minimum Number of Swaps to Make the Binary String Alternating.java

class Solution {
    public int minSwaps(String s) {
        int cntZero=0 , cntOne=0;
        for(char ch:s.toCharArray()){
            if(ch=='0') cntZero++;
            else cntOne++;
        }
        
        //Invalid
        if(Math.abs(cntOne-cntZero)>1) return -1;
        
        
        if(cntOne>cntZero){  //one must be at even posotion
            return countSwaps(s,'1');    
        }else if(cntOne<cntZero){
            return countSwaps(s,'0'); //zero must be at even position
        }
        
        return Math.min(countSwaps(s,'0'),countSwaps(s,'1'));    
    }
    
    //wrong count 
    private int countSwaps(String s,char start){
        int wrongPosition=0;
        for(int i=0;i<s.length();i+=2){
            if(s.charAt(i)!=start) wrongPosition++;
        }
        return wrongPosition;
    }
}