C Program for Infix to Postfix Conversion. Here we covert the infix expression to postfix expression by using stack. for example a*b-c/d is the infix expression, and equivalent postfix expression is: ab*cd/-. Read more about C Programming Language .

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#define SIZE 50            /* Size of Stack */
#include <ctype.h>
char s[SIZE];
int top = -1; /* Global declarations */

push(char elem) { /* Function for PUSH operation */
 s[++top] = elem;
}

char pop() { /* Function for POP operation */
 return (s[top--]);
}

int pr(char elem) { /* Function for precedence */
 switch (elem) {
 case '#':
  return 0;
 case '(':
  return 1;
 case '+':
 case '-':
  return 2;
 case '*':
 case '/':
  return 3;
 }
}

main() { /* Main Program */
 char infx[50], pofx[50], ch, elem;
 int i = 0, k = 0;
 printf("nnRead the Infix Expression ? ");
 scanf("%s", infx);
 push('#');
 while ((ch = infx[i++]) != '