1from math import gcd
2
3def fractionAddition(expression: str) -> str:
4    def lcm(a, b):
5        return a * b // gcd(a, b)
6
7    num, denom = 0, 1
8    i, n = 0, len(expression)
9    
10    while i < n:
11        sign = 1
12        if expression[i] in '+-':
13            sign = -1 if expression[i] == '-' else 1
14            i += 1
15        j = i
16        while expression[j] != '/':
17            j += 1
18        num1 = int(expression[i:j]) * sign
19        i = j + 1
20        j = i
21        while j < n and expression[j].isdigit():
22            j += 1
23        denom1 = int(expression[i:j])
24        i = j
25
26        common_denom = lcm(denom, denom1)
27        num = num * (common_denom // denom) + num1 * (common_denom // denom1)
28        denom = common_denom
29
30    gcd_ = gcd(abs(num), denom)
31    return f"{num // gcd_}/{denom // gcd_}"

1
public class Solution {
    public string FractionAdditionConsec(string expression) {
        int num = 0, den = 1, n, d;
        int i = 0, sign = 1;

        while (i < expression.Length) {
            if (expression[i] == '+' || expression[i] == '-') {
                sign = (expression[i] == '-') ? -1 : 1;
                i++;
            }

            int numBegin = i;
            while (expression[i] != '/') i++;
            n = int.Parse(expression.Substring(numBegin, i - numBegin));
            n *= sign;
            i++;

            int dBegin = i;
            while (i < expression.Length && Expression[i] >= '0' && expression[i] <= '9') i++;
            d = int.Parse(expression.Substring(dBegin, i - dBegin));

            int lcmDenom = den * (d / GCD(den, d));
            num = num * (lcmDenom / den) + n * (lcmDenom / d);
            den = lcmDenom;
        }

        int gcd = GCD(Math.Abs(num), den);
        return (num / gcd) + "/" + (den / gcd);
    }

    private int GCD(int a, int b) {
        return b == 0 ? a : GCD(b, a % b);
    }
}