"Data structure and algorithm analysis--c language description" after reading Note 5

Converts an infix expression to a suffix expression and outputs, and then computes the value of the suffix expression.

Program:

#include <stdio.h> #include <string.h> #include <stdlib.h> #include "stack.h" char* infix_to_ Postfix (CHAR*&NBSP;STR) {    int i,j=0;    int size=strlen ( STR);     if (str==null)     {printf ("Empty string!!! \ n "); Return null;    }    stack s=createstack (SIZE);     char *tmpstr=malloc (sizeof (char) * (size+1));     if (Tmpstr==null)     {printf ("tmpstr is empty!\n"); return null;    }     for (i=0;i<size;++i)     {if (str[i]== ' + ') {     while (! IsEmpty (s)  && top (s)! = ' ('  )     {tmpstr[j++]=topandpop (s);           }    push (' + ', s);   }else  if (str[i]== '-') {&NBSP;&NBSP;&NBSp; while (! IsEmpty (s)  && top (s)! = ' ('  )     { tmpstr[j++]=topandpop (s);     }    push ('-', s);} Else if (str[i]== ' * ') {    while (! IsEmpty (s)  &&  (Top (s) = = ' * '  | |  top (s) = = '/')  )       {tmpstr[j++]=topandpop (s);      }    push (' * ', s);} Else if (str[i]== '/') {    while (! IsEmpty (s)  &&  (Top (s) = = ' * '  | |  top (s) = = '/')  )     {tmpstr[j++]=topandpop (s);    }     push ('/', s);}   else if (str[i]== ' (') {    push (str[i],s);}   else if (str[i]== ') ' {    while (Top (s)! = ' (')     { Tmpstr[j++]=topandpop (s);     }    pop (s);} else{    tmpstr[j++]=Str[i];}     }    while (! IsEmpty (s))     {tmpstr[j++]=topandpop (s);    }     Return tmpstr;} Void compute (char *goal) {    int i,pre,next,sum;     Stack s=createstack (strlen (goal));     if (S==null) return ;     push (goal[0],s);     push (goal[1],s);     for (I=2;i<strlen (goal ); ++i)     {switch (goal[i]) {    case  ' * ':     { Pre=topandpop (s); Next=topandpop (s); sum= (pre-' 0 ') * (next-' 0 '); Push ((char) (sum+ ' 0 '), s);break;    }    case  '/':     {pre=topandpop (s); Next=topandpop (s); sum= (next-' 0 ')/(pre-' 0 '); Push ((char) (sum+ ' 0 '), s);break;    }    case  ' + ':     {pre=topandpop (s); nExt=topandpop (s); sum= (next-' 0 ') + (pre-' 0 '); Push (char) (sum+ ' 0 '), s);break;    }    case  '-':     {pre=topandpop (s); Next=topandpop (s); sum= (next-' 0 ')-(pre-' 0 '); Push ((char) (sum+ ' 0 '), s);break;    }    default:     {push (goal[i],s);break;    }        }     }    printf ("the result is : %d\n", (Top (s)-' 0 '));} Int main () {    char ss[]= "1+2*3+ (4*1+6)";     char* goal =infix_to_postfix (ss);     printf ("the string is :%s\n", goal);     compute (goal);      return 0;}

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One drawback of the above program is that only the calculation of the size of sizeof (char) can be obtained, such as a char of 1 bytes, then the expression can only be evaluated with a maximum of 256. The reason is that the array in the stack used in the compute () function is of type char. If the Infix_to_postfix () function is separated from the compute () function and written in a different. c file, so that the stack they call is of type char and int, then an arbitrary range of expressions can be computed.

"Data structure and algorithm analysis--c language description" after reading Note 5