Data-Structures-And-Algorithms/infix_to_postfix.cpp at master · Moneshwar/Data-Structures-And-Algorithms · GitHub

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# Data-Structures-And-Algorithms
Here I will post my regular DSA problems

// Program to convert infix expression to postfix expression

#include<iostream.h>
#include<string.h>
#include<conio.h>
#include<ctype.h>

char s[20];
int top=-1;

// Function to assign value based on priority

int priority(char c)
{
    if( c == '(' )
             return(0);

    else if( ( c == '+' ) || ( c == '-' ) )
             return(1);

    else if( ( c == '*' ) || ( c == '/' ) )
             return(2);

    return 0;

}

// Pooping the element from the stack

void pop()
{
    if( top == -1 )
         cout << "underflow";
    else
    {
        if( top >= 0 )
        {
            cout << s[top];
            top--;
        }
    }
}

// Pushing the element into the stack based on priority

void push(char d)
{
    if( top == 20 )
        cout << "overflow";
    else
    {
        if( top == -1 )
            s[++top] = d;
        else if( d == '(' )
            s[++top] = d;
        else
        {
            while( priority( s[top] ) >= priority( d ) )
                pop();
            s[++top] = d;
        }
    }
}

int main()
{
    int i,n;
    char a[30];
    cout << "Enter the expression";
    cin >> a;
    n=strlen(a);

    for(i=0;i<n;i++)
    {
        // Checking whether the input is a number or an alphabet

        if( isalnum( a[i] ) )
            cout << a[i];

        else if( a[i] == '(' )
            push( a[i] );

        else if( a[i] == ')' )
        {
            while( s[top] != '(' )
                pop();
            top--;
        }

        else
            push(a[i]);

    }

    while( top >= 0 )
        pop();

        return 0;

}