拆分數字 3 = 2+1，3=1+1+1

數據拆分

例如：5 拆分爲

5 = 4 + 1
5 = 3 + 1 + 1
5 = 2 + 1 + 1 + 1
5 = 1 + 1 + 1 + 1 + 1
5 = 2 + 3

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C#代碼

/// <summary>
/// 數字拆分
/// </summary>
/// <param name="num">要拆分的數字</param>
/// <returns></returns>
private string SumNum(int num)
{
    string str = "";
    if (num <= 1 || num >= int.MaxValue)
    {
        //肯定有效範圍數字不能小於1
        //不能大於int最大值（int最大值 int.MaxValue = 2147483647）
        return str;
    }
    int prv = num - 1;
    while (prv > 0)
    {
        int idx = prv;
        str += num + " = " + prv + " + ";
        while (idx < num)
        {
            if (idx < num - 1)
            {
                str += "1 + ";
            }
            else
            {
                str += "1";
            }
            idx++;
        }
        str += "\r\n";
        prv--;
    }
    prv = 2;
    while (prv <= num / 2)
    {
        str += num + " = " + prv + " + ";
        int sum = 0;
        for (int i = prv; i < num; i++)
        {
            sum += 1;
        }
        str += sum + "\r\n";
        prv++;
    }
    return str;
}