Infix Postfix

[No2024]

program to convert infix expression to postfix expression
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define MAX 20
char STACK[MAX];
int top = -1;
int prcd(char);
void infix2postfix(char[],char[]);
void push(char c) {
STACK[++top] = c;
}
char pop() {
return STACK[top--];
}
int prcd(char x) {
if (x == '^')
return 3;
else if (x == '*' || x == '/')
return 2;
else if (x == '+' || x == '-')
return 1;
else
return 0;
}
void infix2postfix(char infix[], char postfix[]) {
char temp, x;
int i = 0, j = 0;
while (infix[i] != '\0') {
temp = infix[i];
if (isalnum(temp)) {
postfix[j++] = temp;
} else if (temp == '(') {
push(temp);
} else if (temp == ')') {
while ((x = pop()) != '(') {
postfix[j++] = x;
}
} else {
while (top != -1 && prcd(STACK[top]) >= prcd(temp)) {
postfix[j++] = pop();
}
push(temp);
}
i++;
}
while (top != -1) {
postfix[j++] = pop();
}
postfix[j] = '\0';
}
int main() {
char infix[MAX], postfix[MAX];
printf("Enter infix expression: ");
gets(infix);
infix2postfix(infix, postfix);
printf("Postfix expression: %s\n", postfix);
return 0;
}