简单的表达式求值.docx

#include#include#include#define MAXSIZE 20 /*表达式串最大长度 */#define OK 1#define ERROR 0#define TRUE 1#define FALSE 0typedef float Elemtype;typedef struct Elemtype dataMAXSIZE; int top;SqStack; /*定义顺序栈类型*/int InitStack(SqStack &s) /*初始化栈 */ s.top=-1; /*栈顶指针置为-1 */ return OK;int StackEmpty(SqStack s) return (s.top=-1?TRUE:FALSE);int StackFull(SqStack s) return (s.top=MAXSIZE-1?TRUE:FALSE);int Push(SqStack &s, Elemtype e) /*元素进栈*/ if (StackFull(s) return ERROR; s.top+; s.datas.top=e; return OK;int Pop(SqStack &s, Elemtype &e) /*元素出栈，并保存栈顶元素*/ if (StackEmpty(s) return ERROR; e=s.datas.top; s.top-; return OK;Elemtype GetTop(SqStack s) /*取栈顶元素*/ Elemtype e; e=s.datas.top; return e;Elemtype Operate (Elemtype a,char theta,Elemtype b) /*进行相应运算并得到结果*/ Elemtype z; switch (theta) case +:z=a+b;break; case -:z=a-b;break; case *:z=a*b;break; case /:z=a/b;break; return(z);char Precede (char a,char b) /*比较两个运算符的优先级*/ char z; if(b=+)|(b=-)|(b=*)|(b=/)|(b=()|(b=)|(b=)switch (a)case +: case -: if(b=*)|(b=/)|(b=() z=; break; case *: case /: if(b=() z=;break; case (: if(b=) z=e; else if(b=)z=; else z=; break; case =: if(b=)z=; else if(b=) z=e; else z=;break; else z=e; return(z);int In(char ch) /*判断字符是否为运算符*/ int i,flag=0; char opn7=+,-,*,/,(,),=; /*算符数组*/ for (i=0;i=0&*p=0&*p0) k+;p+; if (k0) u=u/(Elemtype)pow(10,k-1); /10的k-1次方 Push (OPND,(Elemtype)u); /*将数字字符转换成相应数值进OPND栈*/else switch(Precede (char)GetTop(OPTR),*p) case :Pop(OPTR,theta); /*将操作符thera出栈，此时它为float型*/ Pop(OPND,b); /*将右操作数出栈*/Pop(OPND,a); /*将左操作数出栈*/Push(OPND,Operate(a,(char)theta,b) ;break;case e: printf(表达式有误!);exit(1); x=GetTop(OPND); return x;int main() char exprMAXSIZE; InputFormul