Solution10.java

class Solution10 {
    public String fractionAddition(String expression) {
        long x = 0, y = 1; 
        int index = 0, n = expression.length();
        while (index < n) {
            
            long x1 = 0, sign = 1;
            if (expression.charAt(index) == '-' || expression.charAt(index) == '+') {
                sign = expression.charAt(index) == '+' ? 1 : -1;
                index++;
            }
            while (index < n && Character.isDigit(expression.charAt(index))) {
                x1 = x1 * 10 + expression.charAt(index) - '0';
                index++;
            }
            x1 = sign * x1;

            
            long y1 = 1; 
            if (index < n && expression.charAt(index) == '/') {
                index++; 
                y1 = 0;
                while (index < n && Character.isDigit(expression.charAt(index))) {
                    y1 = y1 * 10 + expression.charAt(index) - '0';
                    index++;
                }
            }

            x = x * y1 + x1 * y;
            y *= y1;
        }
        if (x == 0) {
            return "0/1";
        }
        long g = gcd(Math.abs(x), Math.abs(y)); 
        return Long.toString(x / g) + "/" + Long.toString(y / g);
    }

    public long gcd(long a, long b) {
        long remainder = a % b;
        while (remainder != 0) {
            a = b;
            b = remainder;
            remainder = a % b;
        }
        return b;
    }
}