栈求表达式的问题,看不太懂,大侠们帮忙把注释添上~(详细些)~
如题,谢谢!!
#define N 50
#define OK 1
#define ERROR 0
#include <ctype.h>
#include <string.h>
typedef struct{
int top;
double array[N];
}NumStack;
typedef struct{
int top;
char array[N];
}OpStack;
int Cint(char mychar){
return (mychar-48);
}
void PushNum(NumStack *numstack,double num){
numstack->top++;
numstack->array[numstack->top-1]=num;
}
void PopNum(NumStack *numstack,double *num){
*num=numstack->array[numstack->top-1];
numstack->top--;
}
void PushOp(OpStack *opstack,char op){
opstack->top++;
opstack->array[opstack->top-1]=op;
}
void PopOp(OpStack *opstack,char *op){
*op=opstack->array[opstack->top-1];
opstack->top--;
}
double Calc(double a,double b,char c){
double result;
switch(c){
case '+':result=a+b;break;
case '-':result=a-b;break;
case '*':result=a*b;break;
case '/':result=a/b;break;
}
return result;
}
char Priority(char y,char x){
char priority='<';
switch(x){
case '+':
case '-':if(y=='(' || y=='#')priority='>';break;
case '*':
case '/':if(y=='(' || y=='#'|| y=='+' || y=='-')priority='>';break;
case '(':priority='>';break;
case ')':if(y=='(')priority='=';break;
case '#':if(y=='#')priority='=';break;
default:priority='E';
}
return priority;
}
void Process(NumStack *numstack,OpStack *opstack,char x){
double a,b;char c;
static double tempnum=0.00000000;static int len=10;static int dot=0,flags=0;
if(isdigit(x)|| x=='.'){
if(x=='.')dot=1;
else{
if(dot==0)
tempnum=tempnum*10+Cint(x);
else{
tempnum=tempnum+(double)Cint(x)/len;
len*=10;
}
}
}
else{
if(flags==0 && x!='('){PushNum(numstack,tempnum);tempnum=0.00000000;len=10;dot=0;}
switch(Priority(opstack->array[opstack->top-1],x)){
case '>':PushOp(opstack,x);flags=0;break;
case '<':
PopOp(opstack,&c);
PopNum(numstack,&b);
PopNum(numstack,&a);
PushNum(numstack,Calc(a,b,c));flags=1;
Process(numstack,opstack,x);break;
case '=':PopOp(opstack,&c);flags=1;break;
default:printf("Wrong Express!");exit(0);
}
}
}
main(){
NumStack numstack;
OpStack opstack;
char s[N];
int i=0;
numstack.top=0;
opstack.top=0;
PushOp(&opstack,'#');
printf("\nEnter your expression and end it with #:");
scanf("%s",s);
for(i=0;i<strlen(s);i++)
Process(&numstack,&opstack,s[i]);
printf("The result is %f",numstack.array[numstack.top-1]);
getch();
}
[解决办法]
这里有功能更强大的，且有注释。
可进行加减乘除、乘方、开方（即M/N次方）、阶乘、sin、cos/tan/exp/log/等函数计算，函数功能还可以自行扩展。
http://blog.csdn.net/zhw952/archive/2010/04/27/5536627.aspx
