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    public int solve(String nums) {
        
        if (nums == null || nums.length() == 0 || nums.charAt(0) == '0') {
            return 0;
        }

        int n = nums.length();
        
        int prevPrev = 1; 
        int prev = 1;

        for (int i = 2; i <= n; i++) {
            int curr = 0;
            char currChar = nums.charAt(i - 1);
            char prevChar = nums.charAt(i - 2);

            
            if (currChar != '0') {
                curr += prev;
            }

            
            int twoDigit = Integer.parseInt(nums.substring(i - 2, i));
            if (twoDigit >= 10 && twoDigit <= 26) {
                curr += prevPrev;
            }

            
            prevPrev = prev;
            prev = curr;
        }

        return prev;
    }