Sliding Window Approach

class Solution {
    public int smallestSubstring(String S) {
        // Code here
        int shubhcode = Integer.MAX_VALUE;
        int n = S.length();
        
        int left = 0;
        int right = 0;
        int one = 0;
        int two = 0;
        int zero = 0;
        while (right < n && left < n) {
            zero += S.charAt(right)=='0' ? 1 : 0;
            one += S.charAt(right)=='1' ? 1 : 0;
            two += S.charAt(right)=='2' ? 1 : 0;
            
            while (left < right && zero >= 1 && one >= 1 && two >= 1) {
                shubhcode = Math.min(shubhcode, (right-left+1));
                zero += S.charAt(left)=='0' ? -1 : 0;
                one += S.charAt(left)=='1' ? -1 : 0;
                two += S.charAt(left)=='2' ? -1 : 0;
                left++;
            } 
            
            right++;
        }
        
        
        
        return shubhcode == Integer.MAX_VALUE ? -1 : shubhcode;
    }
};