数据结构（表达式求值） c语言

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#define MAXSIZE 100
#define set_num 8

typedef struct {
	char *base;
	int top;
	int stacksize;
}sqstackc;//构造字符栈

typedef struct{
	double *base;
	int top;
	int stacksize;
}sqstackd;//构造数字栈

void initstackc(sqstackc *s){//初始化字符数组 
	s->base=(char*)malloc(MAXSIZE * sizeof(char));
	s->top=0;
	s->stacksize=MAXSIZE;
}

void initstackd(sqstackd *s){
	s->base=(double*)malloc(MAXSIZE *sizeof(double));
	s->top=0;
	s->stacksize=MAXSIZE;
}

int stackcempty(sqstackc *s){
	if(s->top==0) return 1;
	else return 0;
}

int stackdempty(sqstackd *s){
	if(s->top==0) return 1;
	else return 0;
}

int stackcfull(sqstackc *s){
	if(s->top>=s->stacksize) return 1;
	else return 0 ;
}

int stackdfull(sqstackd *s){
	if(s->top>=s->stacksize) return 1 ;
	else return 0; 
}

int pushc(sqstackc *s,char x){
	if(stackcfull(s)) return 0;
	else {
		s->base[s->top]=x;
		s->top++;
	}
}

int pushd(sqstackd *s,double x){
	if(stackdfull(s)) return 0;
	else{
		s->base[s->top]=x;
		s->top++;
	}
}

char popc(sqstackc *s){
	char x;
	if(stackcempty(s)) return 0 ;
	else{
		x=s->base[s->top-1];
		s->top--;
		return x;
	}
} 

double popd(sqstackd *s){
	double x;
	if(stackdempty(s)) return 0;
	else {
		x=s->base[s->top-1];
		s->top--;
		return x;
	}
}

//字符优先级数表 
unsigned char prior[8][8] =

              {

                   /* '+' '-'  '*'  '/' '('  ')'  '#' '^' */

               /*'+'*/'>', '>', '<', '<', '<','>', '>', '<',

               /*'-'*/'>', '>', '<', '<', '<','>', '>', '<',

               /*'*'*/'>', '>', '>', '>', '<','>', '>', '<',

               /*'/'*/'>', '>', '>', '>', '<','>', '>', '<',

               /*'('*/'<', '<', '<', '<', '<','=', ' ', '<',

               /*')'*/'>', '>', '>', '>', ' ','>', '>', '>',

               /*'#'*/'<', '<', '<', '<', '<',' ', '=', '<',

               /*'^'*/'>', '>', '>', '>', '<','>', '>', '>'

              };
              
unsigned char priorset[8]={'+','-','*','/','(',')','#','^'};

int findinset(char c){
	int i;
	for(i=0;i<8;i++){
		if(c==priorset[i]) return i;
	}
}

char compare(char op,char c){
	int i,j;
	i=findinset(op);
	j=findinset(c);
	return prior[i][j];
}

double operate(double a,char c,double b){
	switch(c){
		case '+':return a+b;
		case '-':return a-b;
		case '*':return a*b;
		case '/':return a/b;
		case '^':return pow(a,b); 
	}
}

char gettop(sqstackc *s){
	char x;
	x=s->base[s->top-1];
	return x;
}
int main(void){
	double x,a,b;
	sqstackc *note;
	note=(sqstackc *)malloc(sizeof(sqstackc));
	initstackc(note);
	pushc(note,'#');
	sqstackd *num;
	num=(sqstackd *)malloc(sizeof(sqstackd));
	initstackd(num);
	char ch;
	ch=getchar();
	while(ch!='#'||gettop(note)!='#'){
		if(ch>='0'&&ch<='9'){
			x=ch-'0';
			pushd(num,x);
			ch=getchar();
		}
		else{
			switch(compare(gettop(note),ch)){
				case '<':pushc(note,ch);ch=getchar();break;
				case '=':
					popc(note);
					ch=getchar();
					break;
				case '>':
					b=popd(num);
					a=popd(num);
					a=operate(a,popc(note),b);
					pushd(num,a);
					break;
			}
		}
	}
	printf("%lf",num->base[num->top-1]);
} 

用得是后缀式。