栈和应用_表达式求值

#include<stdio.h>#include<stdlib.h>#include<ctype.h>#include<malloc.h>#include<limits.h>#include<io.h>#include<math.h>#include<process.h>//函数结果状态代码#define TRUE 1#define FALSE 0#define OK 1#define ERROR 0#define INFEASIBLE -1#define Stack_Init_Size 10#define StackIncrement 2//#define OVERFLOW -1 //在math.h 中已定义OVERFLOW 等于3typedef int Status;typedef int Boolean;typedef int SElemType;typedef struct sqstack//结构体{SElemType * base ;SElemType * top ;int stacksize ;//栈的大小}SqStack,*PSqStack;Status Init(SqStack &S){//初始化栈S.base = (SElemType *)malloc(Stack_Init_Size * sizeof(SElemType));if (!S.base) exit(OVERFLOW);//存分配不足S.top = S.base;//栈为空S.stacksize = Stack_Init_Size ;return OK;}Status DestoryStack(SqStack &S){//销毁栈free(S.base);S.base = NULL;//预防野指针的出现S.top = NULL;//预防野指针的出现S.stacksize = 0;return OK;}Status StackEmpty(SqStack S){//判断栈是否为空，若空返回TRUE 否则返回FALSEif (S.base == S.top)return TRUE ;elsereturn FALSE ;}Status StackClear(SqStack &S){//清空栈S.top = S.base;return OK;}Status GetTop(SqStack S,SElemType &e){//若栈不为空，则e返回栈顶元素的值，返回值为OK，否则返回值为ERROR if (S.top == S.base) return ERROR;e=*(S.top-1);return OK;}Status Push(SqStack &S,SElemType e){//入栈操操作,入栈元素为eif(S.top-S.base >= S.stacksize)//栈满了的时候{S.base = (SElemType *)realloc(S.base,(S.stacksize+StackIncrement)*sizeof(SElemType));if (!S.base) exit(OVERFLOW);S.top = S.base + S.stacksize;S.stacksize = S.stacksize+StackIncrement;}*(S.top) = e;//栈没满的时候S.top++;return OK;}Status Pop(SqStack &S,SElemType &e){//若栈不空，则删除栈顶元素，用e返回，返回值为OK，否则返回ERRORif(S.top == S.base) return ERROR;S.top--;//top里面没元素e = *(S.top);}void StackTraverse(SqStack S){SElemType * p=S.top-1;// if(S.top == S.base) ;while(p >= S.base){printf("%d ",*p);p--;}}//以上是栈的基本操作//下面的是对表达式的基本操作char Precede(SElemType t1, SElemType t2){//判断t1，t2的优先级('#'代替'\n')，t1、t2是两个运算符char f;switch(t2){case'+':case'-':if(t1 == '(' || t1 == '\n')f ='<';//t1<t2elsef ='>';//t1>t2break;case'*':case'/':if(t1 == '*' || t1 == '/' || t1 == ')')f ='>';//t1>t2elsef ='<';//t1<t2break;case'(':if(t1 == ')'){printf("括号不匹配\n");exit(ERROR);}elsef ='<';//t1<t2break;case')':switch(t1){case'(':f ='=';//t1=t2break;case'\n':printf("缺乏左括号\n");exit(ERROR);default:f ='>';//t1>t2}break;case'\n':switch(t1){case'\n':f ='=';break;case'(':printf("缺乏右括号\n");exit(ERROR);default:f ='>';}}return f;}Status In(SElemType c){//判断c是否为7种运算符之一switch(c){case'+':case'-':case'*':case'/':case'(':case')':case'\n':return TRUE;default:return FALSE;}}SElemType Operate(SElemType a,SElemType theta,SElemType b){//做四则运算a theta b,返回运算结果switch(theta){case'+':return a+b;case'-':return a-b;case'*':return a*b;case'/':return a/b;}}SElemType EvaluateExpression(){//算数表达式求值的算符优先算法。

设OPTR和OPND分别为运算符栈和数字栈SqStack OPTR,OPND;SElemType a,b,c,x;Init(OPTR);Init(OPND);Push(OPTR,'\n');c = getchar();GetTop(OPTR,x);while(c != '\n' || x !='\n'){if(In(c))switch(Precede(x,c)){case'<':Push(OPTR,c);c = getchar();break;case'=':Pop(OPTR,x);c = getchar();break;case'>':Pop(OPTR,x);Pop(OPND,b);Pop(OPND,a);Push(OPND,Operate(a,x,b));}else if(c >= '0' && c <= '9')//c是操作数{Push(OPND,c-48);c = getchar();}else{printf("出现非法字符！\n");exit(ERROR);}GetTop(OPTR,x);}Pop(OPND,x);//弹出运算数栈OPND的栈顶元素给x if(!StackEmpty(OPND)){printf("表达式不正确\n");exit(ERROR);}return x;}int main(){printf("请输入算数表达式（输入的值要在0~9之间，中间运算以及输出结果在-1287~127之间）\n");printf("%d\n",EvaluateExpression());system("pause");return 0;}。