设计并实现将一个中缀表达式转换成逆波兰式,然后对此逆波兰表达式求值的算法。

/* Note:Your choice is C IDE */

#include "stdio.h"

#include "stdlib.h"

#include "string.h"

#define STACK_INIT_SIZE 100 //初始大小#define STACK_INCR_SIZE 10 //增加大小

#define OVERFLOW -2

typedef char SELemType;

typedef struct{

SELemType base[STACK_INIT_SIZE];

int top;

}SqStack;

void InitStack(SqStack *s) //初始化{

s->top=-1;

}

void Push(SqStack *s,SELemType e) //进栈{

if(s->top==STACK_INIT_SIZE-1)

exit(OVERFLOW);

else

s->base[++s->top]=e;

}

void Pop(SqStack *S, SELemType *e) //删除栈顶元素{

if (S->top==-1)

exit(OVERFLOW);

else

*e=S->base[S->top--];

}

char GetTop(SqStack S) //取栈顶元素

{

SELemType e;

if (S.top == -1)

exit(OVERFLOW);

else

e=S.base[S.top];

return e;

}

SELemType Operate(SELemType a[],SELemType O,SELemType b[])

{

char str[10];

int m=0,n=0,result,i=0,j=0,O,R;

while(a[i]!='\0')

{

m=m*10+(a[i]-'0');

i++; }

while(b[j]!='\0')

{

n=n*10+(b[j]-'0');

j++; }

O='+';

switch(O)

{

case '+':

result=m+n;break; case '-':

result=m-n;break; case '*':

result=m*n;break; case '/':

result=m/n;break; }

R=result;

i=0;

do{

result=result/10;

i++;

}while(result>0);

for(j=i-1;j>=0;j--)

{

result=R%10;

R=R/10;

str[j]=(result+'0');

}

str[i]='\0';

return str;

}

SELemType Precede(SELemType a,SELemType b) {

int m,n;

SELemType operat[7][7]={'>','>','<','<','<','>','>',

'>','>','<','<','<','>','>',

'>','>','>','>','<','>','>',

'>','>','>','>','<','>','>',

'<','<','<','<','<','=',' ',

'>','>','>','>',' ','>','>',

'<','<','<','<','<',' ','=',}; switch(a)

{

case '+':

m=0;break;

case '-':

m=1;break;

case '*':

m=2;break;

case '/':

m=3;break;

case '(':

m=4;break;

case ')':

m=5;break;

case '#':

m=6;break;

}

switch(b)

{

case '+':

n=0;break;

case '-':

n=1;break;

case '*':

n=2;break;

case '/':

n=3;break;

case '(':

n=4;break;

case ')':

n=5;break;

case '#':

n=6;break;

}

return operat[m][n];

}

char EvaluateExpression() {

SqStack OPND,OPTR;

char c,x,theta; char a,b;

int i=0,j;

InitStack(&OPTR); Push(&OPTR,'#');

InitStack(&OPND); c=getchar();

while(c!='#'||GetTop(OPTR)!='#') {

if(c!='+'&&c!='-'&&c!='*'&&c!='/'&&c!='('&&c!=')'&&c!=' #')

{ Push(&OPND,c);

str[i]=c;

i++;

c=getchar();

}

else

switch (Precede(GetTop(OPTR),c))

{ case '<': Push(&OPTR,c);

c=getchar();

break;

case '=': Pop(&OPTR,&x);

c=getchar();

break;

case '>': Pop(&OPTR,&theta);

str[i]=theta;

i++;

Pop(&OPND,&b);

Pop(&OPND,&a);

Push(&OPND,Operate(a,theta,b));

break;

}

}

c=GetTop(OPND);

/* DestroyStack(OPTR);

DestroyStack(OPND);*/

return c;

}

void main()

{

printf("%c",EvaluateExpression()); }