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inf_pref.c
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inf_pref.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define size 100
char stack[size];
char prefix[size];
int top = -1;
void reverseString(char *str) {
int length = strlen(str);
int start = 0;
int end = length - 1;
char temp;
while (start < end) {
temp = str[start];
str[start] = str[end];
str[end] = temp;
start++;
end--;
}
}
void push(char character)
{
top++;
stack[top] = character;
}
char pop()
{
char del_element;
del_element = stack[top];
top--;
return del_element;
}
int is_operator(char ch)
{
return (ch == '+' || ch == '-' || ch == '*' || ch == '/' || ch == '^');
}
int precedence(char ch)
{
if (ch == '+' || ch == '-')
{
return 1;
}
else if (ch == '*' || ch == '/')
{
return 2;
}
else if (ch == '^')
{
return 3;
}
return 0;
}
void main()
{
char infix[size];
printf("Enter the infix expression:\n");
fgets(infix, size - 1, stdin);
infix[strlen(infix) - 1] = '\0';
reverseString(infix);
int i,j=0;
for (i = 0; infix[i] != '\0'; i++)
{
char symbol = infix[i];
if (symbol == '(')
{
while (stack[top] != ')')
{
prefix[j]=pop();
j++;
}
pop();
}
else if (symbol == ')')
{
push(symbol);
}
else if (is_operator(symbol))
{
while (top >= 0 && precedence(stack[top]) > precedence(symbol))
{
prefix[j]=pop();
j++;
}
push(symbol);
}
else
{
prefix[j]=symbol;
j++;
}
}
while (top >= 0)
{
prefix[j]=pop();
j++;
}
reverseString(prefix);
puts(prefix);
}
/*
Enter the infix expression:
a+b*c/d^e^(f-g)
+a/*bc^^de-fg
*/