idk why these stuffs get stashed for so long and I didn't ever commit them

OrigFiles/3-特殊线性表/EvaluateExpression(表达式计算)/EvaluateExpression.cpp

@@ -0,0 +1,147 @@
+/***链栈实现表达式求值***/
+#include<iostream>
+#include<string>
+using namespace std;
+
+const char oper[7] = {'+','-','*','/','(',')','#'};
+#define OK 1
+#define ERROR 0
+#define OVERFLOW -2
+typedef char SElemType;
+typedef int Status;
+typedef struct SNode{
+	int data;
+	struct SNode *next;
+}SNode,*LinkStack;
+
+Status InitStack(LinkStack &S)
+{
+	S = NULL;
+	return OK;
+}
+bool StackEmpty(LinkStack S)
+{
+	if(!S)
+		return true;
+	return false;
+}
+Status Push(LinkStack &S,SElemType e)
+{
+	SNode *p = new SNode;
+	if(!p)
+	{
+		return OVERFLOW;
+	}
+	p->data = e;
+	p->next = S;
+	S = p;
+	return OK;
+}
+Status Pop(LinkStack &S,SElemType &e)
+{
+	SNode *p;
+	if(!S)
+		return ERROR;
+	e = S->data;
+	p = S;
+	S = S->next;
+	delete p;
+	return OK;
+}
+Status GetTop(LinkStack &S,SElemType &e)
+{
+	if(!S)
+		return ERROR;
+	e = S->data;
+	return OK;
+}
+bool In(char ch)
+{//判断ch是否为运算符
+	for(int i = 0;i < 7;i ++)
+	{
+		if(ch == oper[i])
+		{
+			return true;
+		}
+	}
+	return false;
+}
+char Precede(char theta1,char theta2)
+{//判断运算符优先级
+	if((theta1 == '('&&theta2 == ')')||(theta1 == '#'&&theta2 == '#'))
+	{
+		return '=';
+	}
+	else if(theta1 == '('||theta1 == '#'||theta2 == '('
+		||(theta1 == '+'||theta1 == '-')&&(theta2 == '*'||theta2 == '/'))
+	{
+		return '<';
+	}
+	else
+		return '>';
+}
+char Operate(char first,char theta,char second)
+{//计算两数运算结果
+	switch(theta)
+	{
+	case '+':
+		return (first - '0')+(second - '0')+48;
+	case '-':
+		return (first - '0')-(second - '0')+48;
+	case '*':
+		return (first - '0')*(second - '0')+48;
+	case '/':
+		return (first - '0')/(second - '0')+48;
+	}
+	return 0;
+}
+
+//　表达式求值
+char EvaluateExpression()
+{
+	// 算术表达式求值的算符优先算法。设OPTR和OPND分别为运算符栈和操作数栈，
+	// OP 为运算符集合
+	LinkStack OPTR,OPND;
+	char ch,theta,a,b,x,top;
+	InitStack ( OPTR);
+	Push (OPTR,'#');
+	InitStack ( OPND);
+	ch = getchar();
+	while (ch != '#' || (GetTop(OPTR,top) ,top!= '#') )
+	{
+		if (!In(ch))
+		{
+			Push(OPND, ch);
+			ch = getchar();
+		} // ch不是运算符则进栈
+		else
+			switch (GetTop(OPTR, top),Precede(top,ch))
+			{ //比较OPTR的栈顶元素和ch的优先权
+			case '<': //当前字符ch压入OPTR栈，读入下一字符ch
+				Push(OPTR, ch);
+				ch = getchar();
+				break;
+			case '>': //弹出OPTR栈顶的运算符进行相应运算，并将运算结果入栈
+				Pop(OPTR, theta);
+				Pop(OPND, b);
+				Pop(OPND, a);
+				Push(OPND, Operate(a, theta, b));
+				break;
+			case '=': //脱括号并接收下一字符
+				Pop(OPTR, x);
+				ch = getchar();
+				break;
+			} // switch
+	} // while
+	GetTop(OPND,ch);
+	return ch;
+} // EvaluateExpression
+
+int main()
+{
+	cout<<"请输入要计算的表达式（操作数和结果都在0-9的范围内，以#结束）："<<endl;
+	char res = EvaluateExpression();
+	cout<<"计算结果为"<<res<<endl;
+
+	return 0;
+}