zhengxing.txt

整型表达式求值

正好我做了一个相关的东西,和你说的不太一样,具体你自己看吧!你参考下吧 呵呵 写的不是很好 输入时数字只能是0-9,算式末尾以#结束,因为用的是字符,所以说功能有限,但希望对你有帮助~
#include<cstdio> 
#include<malloc.h> 
#define NULL 0 
typedef struct node{ 
char date; 
struct node *next; 
}SNode; 

SNode *InitStack(){ 
SNode *top; 
top=(SNode *)malloc(sizeof(SNode)); 
top->next=NULL; 
return top; 
} 
void PushOptr(SNode *top,char x){ 
SNode *p; 
p=(SNode *)malloc(sizeof(SNode)); 
p->date=x; 
p->next=top->next; 
top->next=p; 

} 
char PopOptr(SNode *top){ 
SNode *p; 
char x; 
if(top==NULL) 
return NULL; 
p=top->next; 
x=p->date; 
top->next=p->next; 
free(p); 
return x; 
} 
void PushOpnd(SNode *top,char x){ 
SNode *p; 
p=(SNode *)malloc(sizeof(SNode)); 
p->date=x; 
p->next=top->next; 
top->next=p; 
} 
char PopOpnd(SNode *top){ 
SNode *p; 
char x; 
if(top==NULL) 
return NULL; 
p=top->next; 
x=p->date; 
top->next=p->next; 
free(p); 
return x; 
} 
char GetTop(SNode *top){ 

return (top->next)->date; 
} 
int In(char c){ 
int n; 
switch(c){ 
case '+': 
case '-': 
case '*': 
case '/': 
case '(': 
case ')': 
case '#':n=1;break; 
default:n=0;break; 
} 
return n; 
} 
char Precede(char x,char y){ 
int i,j; 
int form[7][7]={{1,1,-1,-1,-1,1,1},{1,1,-1,-1,-1,1,1},{1,1,1,1,-1,1,1},{1,1,1,1,-1,1,1},{-1,-1,-1,-1,-1,0,2},{1,1,1,1,2,1,1},{-1,-1,-1,-1,-1,2,0}}; 
switch(x){ 
case '+':i=0;break; 
case '-':i=1;break; 
case '*':i=2;break; 
case '/':i=3;break; 
case '(':i=4;break; 
case ')':i=5;break; 
case '#':i=6;break; 
} 
switch(y){ 
case '+':j=0;break; 
case '-':j=1;break; 
case '*':j=2;break; 
case '/':j=3;break; 
case '(':j=4;break; 
case ')':j=5;break; 
case '#':j=6;break; 
} 
if(form[i][j]==1) 
return '>'; 
else 
if(form[i][j]==-1) 
return '<'; 
else 
return '='; 

} 
int Operate(char x,char z,char y){ 
int a=x-'0',b=y-'0'; 
switch(z){ 
case '+':return a+b; 
case '-':return a-b; 
case '*':return a*b; 
case '/':return a/b; 
} 
} 
char Eval_Exp(){ 
char a,b,c,r,f,z; 
int result; 
SNode *top[2]; 
top[0]=InitStack(); 
PushOptr(top[0],'#'); 
top[1]=InitStack(); 
c=getchar(); 
while(c!='#'||(GetTop(top[0]))!='#'){ 
if(!In(c)){ 
PushOpnd(top[1],c); 
c=getchar(); 
} 
else{ 
r=Precede(GetTop(top[0]),c); 
switch(r){ 
case '<':PushOptr(top[0],c); 
c=getchar(); 
break; 
case '=':PopOptr(top[0]); 
c=getchar(); 
break; 
case '>':b=PopOptr(top[0]); 
a=PopOpnd(top[1]); 
z=PopOpnd(top[1]); 
result=Operate(z,b,a); 
f=result+'0'; 
PushOpnd(top[1],f); 
break; 
} 

} 
} 
return f; 
} 
void main(){ 
char result; 
result=Eval_Exp(); 
printf("%d\n",result-'0'); 

}