#include<stdio.h>
#include<math.h>
#define max 100
char ex[max];
void trans(){
char str[max];
char stack[max];
char ch;
int sum,i,j,t,top=0;
printf("*****************************************\n");
printf("*输入一个求值的表达式,以#结束。*\n");
printf("******************************************\n");
printf("算数表达式:");
i=0;
do{
i++;
scanf("%c",&str[i]);
}while(str[i]!='#' && i!=max);
sum=i;
t=1;i=1;
ch=str[i];i++;
while(ch!='#'){
switch(ch){
case '(':
top++;
stack[top]=ch;
break;
case ')':
while(stack[top]!='('){
ex[t]=stack[top];
top--;
t++;
}
top--;
break;
case '+':
case '-':
while(top!=0&&stack[top]!='('){
ex[t]=stack[top];top--;t++;
}
top++;stack[top]=ch;
break;
case '*':
case '/':
while(stack[top]=='*'||stack[top]=='/'){
ex[t]=stack[top];top--;t++;
}
top++;stack[top]=ch;
break;
case ' ':break;
default:
while(ch>='0'&&ch<='9'){
ex[t]=ch;t++;
ch=str[i];i++;
}
i--;
ex[t]='#';t++;
}
ch=str[i];i++;
}
while(top!=0){
ex[t]=stack[top];t++;top--;
}
ex[t]='#';
printf("\n\t原来表达式:");
for(j=1;j<sum;j++)
printf("%c",str[j]);
printf("\n\t后缀表达式:",ex);
for(j=1;j<t;j++)
printf("%c",ex[j]);
}
void compvalue(){
float stack[max],d;
char ch;
int t=1,top=0;
ch=ex[t];t++;
while(ch!='#'){
switch(ch){
case '+':
stack[top-1]=stack[top-1]+stack[top];
top--;
break;
case '-':
stack[top-1]=stack[top-1]-stack[top];
top--;
break;
case '*':
stack[top-1]=stack[top-1]*stack[top];
top--;
break;
case '/':
if(stack[top]!=0)
stack[top-1]=stack[top-1]/stack[top];
else{
printf("\n\t除零错误!\n");
exit(0);
}
top--;
break;
default:
d=0;
while(ch>='0'&&ch<='9'){
d=10*d+ch-'0';
ch=ex[t];t++;
}
top++;
stack[top]=d;
}
ch=ex[t];t++;
}
printf("\n\t计算结果:%g\n",stack[top]);
}
main(){
trans();
compvalue();
}