public double CalculateByExpression(string expression)
{
Dictionary<string, Fraction> dic = new Dictionary<string, Fraction>();
double result = 0D;
int index = 0;
string key = string.Empty;
string value = string.Empty;
double num = 0D;
string pattern = string.Empty;
string option = string.Empty;
//step1 去除表达式里的空格
expression = Regex.Replace(expression, @"\s+", string.Empty);
//step2 替换第一个数字为分数表示
pattern = @"^(\d+(\.\d+)?)";
Match m = Regex.Match(expression, pattern);
if (m.Success)
{
value = m.Groups[1].Value;
num = double.Parse(value);
key = string.Format("F{0}", index++);
dic[key] = new Fraction
{
Denominator = 1D,
Element = num
};
expression = Regex.Replace(expression, pattern, key);
}
//step3 替换紧贴括号的值为分数表示
pattern = @"\((\d+(\.\d+)?)";
m = Regex.Match(expression, pattern);
while (m.Success)
{
value = m.Groups[1].Value;
num = double.Parse(value);
key = string.Format("F{0}", index++);
dic[key] = new Fraction
{
Denominator = 1D,
Element = num
};
expression = expression.Replace(m.Value, "(" + key);
m = Regex.Match(expression, pattern);
}
//step4 替换+-*/后面跟的值为分数表示
pattern = @"(\+|\-|\*|\/)(\d+(\.\d+)?)";
m = Regex.Match(expression, pattern);
while (m.Success)
{
option = m.Groups[1].Value;
value = m.Groups[2].Value;
num = double.Parse(value);
key = string.Format("F{0}", index++);
dic[key] = new Fraction
{
Denominator = 1D,
Element = num
};
expression = expression.Replace(m.Value, option + key);
m = Regex.Match(expression, pattern);
}
//step5 计算乘除和括号运算
MatchCollection matchs = null;
while (Regex.IsMatch(expression, @"\(|\)|\*\/"))
{
if (flag)
{
return -99999999;
}
pattern = @"(F\d+)(\*|\/)(F\d+)";
while (Regex.IsMatch(expression, pattern))
{
m = Regex.Match(expression, pattern);
key = m.Groups[1].Value;
Fraction f1 = dic[key];
key = m.Groups[3].Value;
Fraction f2 = dic[key];
option = m.Groups[2].Value;
Fraction f = Calculate(f1, f2, option);
key = string.Format("F{0}", index++);
dic[key] = f;
expression = expression.Replace(m.Value, key);
while (Regex.IsMatch(expression, @"\(F\d+\)"))
{
m = Regex.Match(expression, @"\((F\d+)\)");
expression = expression.Replace(m.Value, m.Groups[1].Value);
}
}
//step3 计算括号里的值，并替换掉括号
pattern = @"\((F\d+)(\+|\-)(F\d+)";
while (Regex.IsMatch(expression, pattern))
{
if (flag)
{
return -99999999;
}
m = Regex.Match(expression, pattern);
key = m.Groups[1].Value;
Fraction f1 = dic[key];
key = m.Groups[3].Value;
Fraction f2 = dic[key];
option = m.Groups[2].Value;
Fraction f = Calculate(f1, f2, option);
key = string.Format("F{0}", index++);
dic[key] = f;
expression = expression.Replace(m.Value, "(" + key);
while (Regex.IsMatch(expression, @"\(F\d+\)"))
{
m = Regex.Match(expression, @"\((F\d+)\)");
expression = expression.Replace(m.Value, m.Groups[1].Value);
}
}
}
//step4 重复step2 计算乘除运算
pattern = @"(F\d+)(\*|\/)(F\d+)";
option = string.Empty;
while (Regex.IsMatch(expression, pattern))
{
if (flag)
{
return -99999999;
}
matchs = Regex.Matches(expression, pattern);
foreach (Match match in matchs)
{
key = match.Groups[1].Value;
Fraction f1 = dic[key];
key = match.Groups[3].Value;
Fraction f2 = dic[key];
option = match.Groups[2].Value;
Fraction f = Calculate(f1, f2, option);
key = string.Format("F{0}", index++);
dic[key] = f;
expression = expression.Replace(match.Value, key);
}
}
//step5 重复step3 计算加减运算
pattern = @"(F\d+)(\+|\-)(F\d+)";
while (Regex.IsMatch(expression, pattern))
{
if (flag)
{
return -99999999;
}
matchs = Regex.Matches(expression, pattern);
foreach (Match match in matchs)
{
key = match.Groups[1].Value;
Fraction f1 = dic[key];
key = match.Groups[3].Value;
Fraction f2 = dic[key];
option = match.Groups[2].Value;
Fraction f = Calculate(f1, f2, option);
key = string.Format("F{0}", index++);
dic[key] = f;
expression = expression.Replace(match.Value, key);
}
}
//step6 最后一步 计算结果
key = string.Format("F{0}", index - 1);
Fraction fraction = dic[key];
result = fraction.Element / fraction.Denominator;
return result;
}
/// <summary>
/// 计算两个分数的加减乘除，并返回一个分数表示
/// </summary>
/// <param name="expression"></param>
/// <returns></returns>
private Fraction Calculate(Fraction f1, Fraction f2, string option)
{
Fraction result = new Fraction();
double dencominator = 0D;
switch (option)
{
case "+":
dencominator = CalculateLeaseCommonMultiple(f1.Denominator, f2.Denominator);
f1.Element = (dencominator / f1.Denominator) * f1.Element;
f2.Element = (dencominator / f2.Denominator) * f2.Element;
result.Denominator = dencominator;
result.Element = f1.Element + f2.Element;
break;
case "-":
dencominator = CalculateLeaseCommonMultiple(f1.Denominator, f2.Denominator);
f1.Element = (dencominator / f1.Denominator) * f1.Element;
f2.Element = (dencominator / f2.Denominator) * f2.Element;
result.Denominator = dencominator;
result.Element = f1.Element - f2.Element;
break;
case "*":
dencominator = f1.Denominator * f2.Denominator;
result.Denominator = dencominator;
result.Element = f1.Element * f2.Element;
break;
case "/":
dencominator = f1.Denominator * f2.Element;
result.Denominator = dencominator;
result.Element = f1.Element * f2.Denominator;
break;
}
return result;
}
