/// <summary>
/// 字符串表达式计算
/// </summary>
/// <param name="expression"></param>
/// <returns></returns>
public double ExpressonCalculate(string expression)
{
if (string.IsNullOrEmpty(expression))
{
throw new Exception("表达式不能为空或null");
}
expression = expression.Replace(" ", string.Empty);
if (expression[0] == Operators.Subtraction)
{
expression = "0" + expression;
}
if (!ExpressionValidate(expression))
{
throw new Exception(string.Format("表达式{0}不是有效的表达式,表达式中不能含有非数字或是四则运算符及小括号运算符", expression));
}
if (BaseCalate.IsOperator(expression[expression.Length - 1]))
{
throw new Exception(string.Format("表达式{0}不是有效的表达式,表达式结尾不能为+-*/四种运算符", expression));
}
//return this.Calculator(this.BaseExpressionParse(expression));//测试该函数用
//return this.Calculator(this.BlendExpressionParse(expression));//测试该函数用
return(this.Calculator(this.ExpressionParse(expression)));
}
/// <summary>
/// 树值计算
/// </summary>
/// <param name="root">要计算的节点</param>
/// <returns>节点计算结果值</returns>
private double Calculator(ExpressionNode root)
{
double result = default(double);
double leftValue = default(double);
double rightValue = default(double);
if (root == null)
{
return(result);
}
if (root.Left != null)
{
if (!root.Left.IsLeaf)
{
leftValue = Calculator(root.Left);
}
else
{
leftValue = root.Left.Value;
}
}
if (root.Right != null)
{
if (!root.Right.IsLeaf)
{
rightValue = Calculator(root.Right);
}
else
{
rightValue = root.Right.Value;
}
}
if (!BaseCalate.IsOperator(root.Operator))
{
result = root.Value;
}
else
{
result = BaseCalate.BaseCal(leftValue, rightValue, root.Operator.ToString());
}
return(result);
}
/// <summary>
/// 表达式验证
/// </summary>
/// <param name="expression">需要验证的表达式</param>
/// <returns>验证通过返回true,非法表达式返回false</returns>
private bool ExpressionValidate(string expression)
{
int leftBrackets = 0;
int rightBrackets = 0;
for (int i = 0; i < expression.Length; i++)
{
//左括号计数
if (expression[i] == Operators.LeftBrackets)
{
leftBrackets++;
}
//右括号计数
if (expression[i] == Operators.RightBrackets)
{
rightBrackets++;
}
//如果是数学运算符则跳过
if (BaseCalate.IsMathOperator(expression[i]))
{
continue;
}
//如果不是数学运算符,也不是数字,则返回false,验证不通过
if (expression[i] < '0' || expression[i] > '9')
{
return(false);
}
}
//左括号和右括号数目不一样,则返回false,验证不通过
if (leftBrackets != rightBrackets)
{
return(false);
}
return(true);
}
/// <summary>
/// 仅加法和减法或仅乘法和除法(不能有加减和乘除混合)表达式解析生成树
/// </summary>
/// <param name="expression">要计算的表达式字符串</param>
/// <returns>表达式节点树</returns>
private ExpressionNode BaseExpressionParse(string expression)
{
ExpressionNode root = new ExpressionNode();
int valueStaratIndex = 0;
string value = string.Empty;
char chDefaultValue = default(char);
char currentOperator = chDefaultValue;
for (int i = 0; i < expression.Length; i++)
{
if (BaseCalate.IsOperator(expression[i]))
{
value = expression.Substring(valueStaratIndex, i - valueStaratIndex);
valueStaratIndex = i + 1;
currentOperator = expression[i];
continue;
}
else
{
if (!string.IsNullOrEmpty(value) && currentOperator != chDefaultValue)
{
if (root.Left == null)
{
var lefttLeafNode = new ExpressionNode();
lefttLeafNode.Value = double.Parse(value.Trim());
lefttLeafNode.Parent = root;
root.Operator = currentOperator;
root.Left = lefttLeafNode;
}
else if (root.Left != null && root.Right == null)
{
var rightLeafNode = new ExpressionNode();
rightLeafNode.Value = double.Parse(value.Trim());
rightLeafNode.Parent = root;
root.Right = rightLeafNode;
var parentNode = new ExpressionNode();
parentNode.Operator = currentOperator;
parentNode.Left = root;
root.Parent = parentNode;
root = parentNode;
}
value = string.Empty;
}
}
}
value = expression.Substring(valueStaratIndex, expression.Length - valueStaratIndex);
if (root.Left != null)
{
var endLeaf = new ExpressionNode();
endLeaf.Value = double.Parse(value.Trim());
endLeaf.Parent = root;
root.Right = endLeaf;
}
else
{
root.Value = double.Parse(value.Trim());
}
return(root);
}
/// <summary>
/// 无括号的加减乘除混合表达式运算
/// </summary>
/// <param name="expression">要计算的表达式字符串</param>
/// <returns>表达式节点树</returns>
private ExpressionNode BlendExpressionParse(string expression)
{
int startSubExpressionIndex = 0;
int endSubExpressionIndex = -1;
string subExpression = string.Empty;
double subExpressionValue = 0.0d;
if (expression[0] == Operators.Subtraction)
{
expression = "0" + expression;
}
while (true)
{
for (int i = 0; i < expression.Length; i++)
{
if (expression[i] == Operators.Multiply || expression[i] == Operators.Division)
{
if (i + 1 == expression.Length)
{
endSubExpressionIndex = i + 1;
}
else
{
for (int j = i + 1; j < expression.Length; j++)
{
if (BaseCalate.IsOperator(expression[j]))
{
endSubExpressionIndex = j;
break;;
}
}
if (endSubExpressionIndex == -1)
{
endSubExpressionIndex = expression.Length;
}
}
subExpression = expression.Substring(startSubExpressionIndex, endSubExpressionIndex - startSubExpressionIndex);
subExpressionValue = BaseCalate.BaseCal(subExpression);
expression = expression.Remove(startSubExpressionIndex, endSubExpressionIndex - startSubExpressionIndex);
expression = expression.Insert(startSubExpressionIndex, subExpressionValue.ToString());
endSubExpressionIndex = -1;
break;
}
if (expression[i] == Operators.Add || expression[i] == Operators.Subtraction)
{
startSubExpressionIndex = i + 1;
}
}
if (!expression.Contains(Operators.Multiply) && !expression.Contains(Operators.Division))
{
break;
}
}
ExpressionNode root = BaseExpressionParse(expression);
return(root);
}