/*author.jiang.2010.5.12*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<malloc.h>


#define STACK_INIT_SIZE 10
#define STACKIMCREMENT 2
typedef struct {
    int  *base;
    int  *top;
    int stacksize;
}sqstack;

void initstack(sqstack *s)
{s->base=(int*)malloc(STACK_INIT_SIZE*sizeof(int));
 if(!s->base)  exit(0);
 s->top=s->base;
 s->stacksize=STACK_INIT_SIZE;
}

void gettop(sqstack s,int *e)
{if(s.base==s.top)  return;
 *e=*(s.top-1);
}
 
void push(sqstack *s,int e)
{if(s->base-s->top>=s->stacksize)
{s->base=(int*)realloc(s->base,(s->stacksize+STACKIMCREMENT)*sizeof(int));
 if(!s->base)  exit(-2);
 s->top=s->base+s->stacksize;
 s->stacksize+=STACKIMCREMENT;
}
*s->top++=e;
}

void pop(sqstack *s,int *e)
{if(s->base==s->top) return;
 *e=*--s->top;
}

char precede(char t1,char t2){
    char f;
    switch(t2){
    case '+':
    case '-':
        if(t1=='('||t1=='#')
            f='<';
        else f='>';
        break;
    case '*':
    case '/':
        if(t1=='*'||t1=='/'||t1==')')
            f='>';
        else f='<';
        break;
    case '(':
        if(t1==')'){
            printf("error1\n");
            exit(0);
        }
        else f='<';
        break;
    case ')':
        switch(t1){
        case '(':f='=';break;
        case '#':{printf("error2\n");exit(0);}
        default:f='>';
        }
        break;
    case '#':
        switch(t1){
            case '(':{printf("error3\n");exit(0);}
            case '#':f='=';
            default:f='>';
        }
        break;
    }
    return f;
}

int in(char c){
    switch(c){
    case '+':
    case '-':
    case '*':
    case '/':
    case '(':
    case ')':
    case '#':return 1;
    default:return 0;
    }
}

int operate(int a,char theta,int b){
    int c;
    switch(theta){
    case '+':c=a+b;break;
    case '-':c=a-b;break;
    case '*':c=a*b;break;
    case '/':c=a/b;break;
    }
    return c;
}

int evaluateexpression(){
    sqstack optr,opnd;
    int a,b,i=0,x;
    int d;
    char c,theta;
    char z[6];
    initstack(&optr); push(&optr,'#');
    initstack(&opnd);c=getchar();
    gettop(optr,&x);
    while(c!='#'||x!='#'){
        if(in(c)){
            switch(precede(x,c)){
            case '<':
                push(&optr,c);
                c=getchar();
                break;
            case '=':
                pop(&optr,&x);
                c=getchar();
                break;
            case '>':
                pop(&optr,&theta);
                pop(&opnd,&b);
                pop(&opnd,&a);
                push(&opnd,operate(a,theta,b));
                break;
            }
        }
        else if(c>='0'&&c<='9'){
            i=0;
            do{z[i]=c;
               i++;
               c=getchar();
            }while(c>='0'&&c<='9');
            //z[i]=0;
            d=atoi(z);
            push(&opnd,d);
        }
        else{
            printf("error4\n");
            exit(0);
        }
        gettop(optr,&x);
    }
  gettop(opnd,&x);
  return x;
}


void main(){
   
    printf("input expressions end with '#'\n");
    printf("------------------------------\n");
    printf("reslut=%d\n",evaluateexpression());
    printf("------------------------------\n");
}

#include<stdio.h>(必不可少)
#include<stdlib.h>（exit）
#include<string.h>(getchar())
#include<malloc.h>(malloc,realloc)

这个程序好像有点问题，比如88-1*5算出来结果是错的