leetcode592

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

        private int LCM(int a, int b)
        {
            return a * b / GCD(a, b);
        }


        public string FractionAddition(string expression)
        {
            var first = expression[0];
            var FU = true;//默认当前表达式为负
            if (first != '-')
            {
                FU = false;//当前表达式为正
            }
            var listPOS = new List<string>();//记录正表达式
            var listNev = new List<string>();//记录负表达式
            //先将正表达式和负表达式分开

            var sb = new StringBuilder();//记录当前表达式

            for (int i = 0; i < expression.Length; i++)
            {
                if (expression[i] == '-')
                {
                    if (FU)
                    {
                        if (sb.Length > 0)
                        {
                            listNev.Add(sb.ToString());
                        }
                    }
                    else
                    {
                        if (sb.Length > 0)
                        {
                            listPOS.Add(sb.ToString());
                        }
                    }
                    FU = true;
                    sb.Clear();
                }
                else if (expression[i] == '+')
                {
                    if (FU)
                    {
                        if (sb.Length > 0)
                        {
                            listNev.Add(sb.ToString());
                        }
                    }
                    else
                    {
                        if (sb.Length > 0)
                        {
                            listPOS.Add(sb.ToString());
                        }
                    }
                    FU = false;
                    sb.Clear();
                }
                else
                {
                    sb.Append(expression[i]);
                }
            }

            if (FU)
            {
                if (sb.Length > 0)
                {
                    listNev.Add(sb.ToString());
                }
            }
            else
            {
                if (sb.Length > 0)
                {
                    listPOS.Add(sb.ToString());
                }
            }


            var listPOSSP = new List<List<int>>();
            foreach (var str in listPOS)
            {
                var ary = str.Split('/');
                var tp = new List<int>();
                tp.Add(int.Parse(ary[1]));
                tp.Add(int.Parse(ary[0]));
                listPOSSP.Add(tp);
            }

            var listNEVSP = new List<List<int>>();
            foreach (var str in listNev)
            {
                var ary = str.Split('/');
                var tp = new List<int>();
                tp.Add(int.Parse(ary[1]));
                tp.Add(int.Parse(ary[0]));
                listNEVSP.Add(tp);
            }

            var lcm1 = 1;
            var sumPOS = 0;
            if (listPOSSP.Any())
            {
                if (listPOSSP.Count == 1)
                {
                    lcm1 = listPOSSP[0][0];
                }
                else
                {
                    lcm1 = listPOSSP[0][0];
                    for (int i = 1; i < listPOSSP.Count; i++)
                    {
                        var curFM = listPOSSP[i][0];
                        lcm1 = LCM(lcm1, curFM);
                    }
                }

                for (int i = 0; i < listPOSSP.Count; i++)
                {
                    var FM = listPOSSP[i][0];
                    var FZ = listPOSSP[i][1];
                    var bs = lcm1 / FM;
                    FZ = FZ * bs;
                    sumPOS += FZ;
                }
            }

            var lcm2 = 1;
            var sumNEV = 0;
            if (listNEVSP.Any())
            {
                if (listNEVSP.Count == 1)
                {
                    lcm2 = listNEVSP[0][0];
                }
                else
                {
                    lcm2 = listNEVSP[0][0];
                    for (int i = 1; i < listNEVSP.Count; i++)
                    {
                        var curFM = listNEVSP[i][0];
                        lcm2 = LCM(lcm2, curFM);
                    }
                }
                
                for (int i = 0; i < listNEVSP.Count; i++)
                {
                    var FM = listNEVSP[i][0];
                    var FZ = listNEVSP[i][1];
                    var bs = lcm2 / FM;
                    FZ = FZ * bs;
                    sumNEV += FZ;
                }
            }

            var lcm = LCM(lcm1, lcm2);
            var bs1 = lcm / lcm1;
            var bs2 = lcm / lcm2;
            var fz1 = sumPOS * bs1;
            var fz2 = sumNEV * bs2;
            var fz = fz1 - fz2;

            var cc = GCD(fz, lcm);
            if (cc < 0)
            {
                cc = cc * -1;
            }
            var result = fz / cc + "/" + lcm / cc;
           
            return result;
        }
}

https://leetcode.com/problems/fraction-addition-and-subtraction/#/description