C# 或Java 怎么實(shí)現(xiàn)類似 傳入6 得到 3-3,2-4,1-5 ，傳入5得到2-3,1-4這樣的效果

public List<AutoCompleteGroup> SetAchieveArithmetic(int groupNumber)
{
            List<AutoCompleteGroup> autoCompleteList = new List<AutoCompleteGroup>();
            if (groupNumber % 2 == 0)   //偶數(shù)
            {
                int number = groupNumber / 2;
                for (int i = 0; i < number; i++)
                {
                    number = number - i;
                    AutoCompleteGroup autoComplete = new AutoCompleteGroup();
                    autoComplete.GradeType = i;
                    autoComplete.Number1 = number;
                    autoComplete.Number2 = groupNumber - autoComplete.Number1;
                    autoCompleteList.Add(autoComplete);
                }
            }
            else //奇數(shù)
            {
                int number = (groupNumber - 1) / 2;
                for (int i = 0; i < number; i++)
                {
                    number = number - i;
                    AutoCompleteGroup autoComplete = new AutoCompleteGroup();
                    autoComplete.GradeType = i;
                    autoComplete.Number1 = number;
                    autoComplete.Number2 = groupNumber - autoComplete.Number1;
                    autoCompleteList.Add(autoComplete);
                }
            }
            return autoCompleteList;
        }
                
                
public class AutoCompleteGroup
 {
        /// <summary>
        /// 優(yōu)先等級(jí) 0為最高
        /// </summary>
        public int GradeType { get; set; }

        /// <summary>
        /// 成團(tuán)數(shù)1        
        /// </summary>
        public int Number1 { get; set; }

        /// <summary>
        /// 成團(tuán)數(shù)2
        /// </summary>
        public int Number2 { get; set; }
}

這樣子寫存在 如果傳入6 只能計(jì)算出 3-3 2-4 , 1-5出不來，誰能優(yōu)化一下