C program to convert infix to prefix notation

/*     Infix to prefix notation
written by- Shivam Rana 
Date- 2/4/12          
Users are requested to use a bracket wherever necessary while giving input otherwise
it might give wrong answer     */
#include<stdio.h>
#include<string.h>
int main()
{
int i,j,l,m,k=0;
char a[400],b[400],reva[400],ans[400];
m=-1;
scanf("%s",&a);
l=strlen(a);
	for(i=0;i<l;i++)
	{
		if(a[l-1-i]=='(')
			reva[i]=')';
		else
			if(a[l-1-i]==')')
			reva[i]='(';
		else
		reva[i]=a[l-1-i];
	}
for(j=0;j<l;j++)
{
if(reva[j]=='(')
continue;
else if(reva[j]>64 && reva[j]<91 ||reva[j]>96 && reva[j]<123)
			ans[k++]=reva[j];
else if(reva[j]==')')
{
			ans[k++]=b[m];
m--;
}
else
{
m++;
b[m]=reva[j];
}
}
	for(i=(k-1);i>=0;i--)
		printf("%c",ans[i]);
	printf("\n");

return 0;
}

C program to convert infix notation to postfix notation

/* c prog for infix to postfix conversion
 written by- Shivam Rana */
#include<stdio.h>
#include<string.h>
int main()
{
int i,j,l,m;
char a[400],b[400];
m=-1;
scanf("%s",&a);
l=strlen(a);
for(j=0;j<l;j++)
{
if(a[j]=='(')
continue;
else if(a[j]>64 && a[j]<91 ||a[j]>96 && a[j]<123)
printf("%c",a[j]);
else if(a[j]==')')
{
printf("%c",b[m]);
m--;
}
else
{
m++;
b[m]=a[j];
}
}printf("\n");

return 0;
}

C program to check a mathematical expression for correctness in terms of brackets, using Stack

/* C program to check a mathematical expression for
 correctness in terms of brackets, using Stack
  Written by- Shivam Rana */
#include<stdio.h>
#include<stdlib.h>
 
struct sNode
{
   char data;
   struct sNode *next;
};
 
void push(struct sNode** top_ref, int new_data);
 
int pop(struct sNode** top_ref);
 

int isMatchingPair(char character1, char character2)
{
   if(character1 == '(' && character2 == ')')
     return 1;
   else if(character1 == '{' && character2 == '}')
     return 1;
   else if(character1 == '[' && character2 == ']')
     return 1;
   else
     return 0;
}
 
int areParenthesisBalanced(char exp[])
{
   int i = 0;

   struct sNode *stack = NULL;
 
  
   while(exp[i])
   {
      if(exp[i] == '{' || exp[i] == '(' || exp[i] == '[')
        push(&stack, exp[i]);

      if(exp[i] == '}' || exp[i] == ')' || exp[i] == ']')
      {
 
          
         if(stack == NULL)
           return 0;
 

         else if ( !isMatchingPair(pop(&stack), exp[i]) )
           return 0;
      }
      i++;
   }
 
  
   if(stack == NULL)
     return 1; /*balanced*/
   else
     return 0;  /*not balanced*/
}
 

int main()
{
  char exp[100];
	printf("Enter expression\n");
	scanf("%s",exp);
  if(areParenthesisBalanced(exp))
    printf("\nBalanced ");
  else
    printf("\nNot Balanced ");  \
  getchar();
}   
 

void push(struct sNode** top_ref, int new_data)
{

  struct sNode* new_node =
            (struct sNode*) malloc(sizeof(struct sNode));
 
  if(new_node == NULL)
  {
     printf("Stack overflow \n");
     getchar();
     exit(0);
  }          
 

  new_node->data  = new_data;
 
  
  new_node->next = (*top_ref); 
 
 
  (*top_ref)    = new_node;
}
 

int pop(struct sNode** top_ref)
{
  char res;
  struct sNode *top;
 
  /*If stack is empty then error */
  if(*top_ref == NULL)
  {
     printf("Stack overflow \n");
     getchar();
     exit(0);
  }
  else
  {
     top = *top_ref;
     res = top->data;
     *top_ref = top->next;
     free(top);
     return res;
  }
}

C program to implement stack using linked list

/* Program of stack using linked list*/
# include<stdio.h>
# include<stdlib.h>
void push();
void pop();
void display();
struct node
{
int info;
struct node *link;
} *top=NULL;

int main()
{
int choice;
while(1)
{ printf("1.Push\n");
printf("2.Pop\n");
printf("3.Display\n");
printf("4.Quit\n");
printf("Enter your choice : ") ;
scanf("%d", &choice);

switch(choice)
{
case 1:
push();
break;
case 2:
pop();
break;
case 3:
display();
break;
case 4:
exit(1);
default :
printf("Wrong choice\n");
}/*End of switch */
}/*End of while */
}/*End of main() */

void push(void)
{
struct node *tmp;
int pushed_item;
tmp = (struct node *)malloc(sizeof(struct node));
printf("Input the new value to be pushed on the stack : ");
scanf("%d",&pushed_item);
tmp->info=pushed_item;
tmp->link=top;
top=tmp;
}

void pop(void)
{
struct node *tmp;
if(top == NULL)
printf("Stack is empty\n");
else
{ tmp=top;
printf("Popped item is %d\n",tmp->info);
top=top->link;
free(tmp);
}

}

void display(void)
{ struct node *ptr;
ptr=top;
if(top==NULL)
printf("Stack is empty\n");
else
{
printf("Stack elements :\n");
while(ptr!= NULL)
{
printf("%d\n",ptr->info);
ptr = ptr->link;
}
}
}

C program to implement stack using array

/* Program of stack using array*/
#include<stdio.h>
#define MAX 5
void push();
void pop();
void display();

int top = -1;
int stack_arr[MAX];

int main()
{
int choice;
while(1)
{
printf("1.Push\n");
printf("2.Pop\n");
printf("3.Display\n");
printf("4.Quit\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1 :
 push();
break;
case 2:
pop();
break;
case 3:
display();
break;
case 4:
				break;
default:
printf("Wrong choice\n");
}/*End of switch*/
}/*End of while*/
}/*End of main()*/

void push(void)
{
int pushed_item;
if(top == (MAX-1))
printf("Stack Overflow\n");
else
{
printf("Enter the item to be pushed in stack : ");
scanf("%d",&pushed_item);
top=top+1;
stack_arr[top] = pushed_item;
}
}

void pop(void)
{
if(top == -1)
printf("Stack Underflow\n");
else
{
printf("Popped element is : %d\n",stack_arr[top]);
top=top-1;
}
}

void display(void)
{
int i;
if(top == -1)
printf("Stack is empty\n");
else
{
printf("Stack elements :\n");
for(i = top; i >=0; i--)
printf("%d\n", stack_arr[i] );
}
}

C program to Implement Polynomial Equation Addition in a Single linked list.

    #include<stdio.h>
    #include<stdlib.h>
    #include<conio.h>
    struct link{
    int coeff;
    int pow;
    struct link *next;
    };
    struct link *poly1=NULL,*poly2=NULL,*poly=NULL;
    void create(struct link *node)
    {
    char ch;
    do
    {
    printf("\n enter coeff:");
    scanf("%d",&node->coeff);
    printf("\n enter power:");
    scanf("%d",&node->pow);
    node->next=(struct link*)malloc(sizeof(struct link));
    node=node->next;
    node->next=NULL;
    printf("\n continue(y/n):");
		fflush(stdin);
scanf("%c",&ch);
    }
    while(ch=='y' || ch=='Y');
    }
    void show(struct link *node)
    {
    while(node->next!=NULL)
    {
    printf("%dx^%d",node->coeff,node->pow);
    node=node->next;
    if(node->next!=NULL)
    printf("+");
    }
    }
    void polyadd(struct link *poly1,struct link *poly2,struct link *poly)
    {
    while(poly1->next && poly2->next)
    {
    if(poly1->pow>poly2->pow)
    {
    poly->pow=poly1->pow;
    poly->coeff=poly1->coeff;
    poly1=poly1->next;
    }
    else if(poly1->pow<poly2->pow)
    {
    poly->pow=poly2->pow;
    poly->coeff=poly2->coeff;
    poly2=poly2->next;
    }
    else
    {
    poly->pow=poly1->pow;
    poly->coeff=poly1->coeff+poly2->coeff;
    poly1=poly1->next;
    poly2=poly2->next;
    }
    poly->next=(struct link *)malloc(sizeof(struct link));
    poly=poly->next;
    poly->next=NULL;
    }
    while(poly1->next || poly2->next)
    {
    if(poly1->next)
    {
    poly->pow=poly1->pow;
    poly->coeff=poly1->coeff;
    poly1=poly1->next;
    }
    if(poly2->next)
    {
    poly->pow=poly2->pow;
    poly->coeff=poly2->coeff;
    poly2=poly2->next;
    }
    poly->next=(struct link *)malloc(sizeof(struct link));
    poly=poly->next;
    poly->next=NULL;
    }
    }
   int main()
    {
    char ch;
    do{
    poly1=(struct link *)malloc(sizeof(struct link));
    poly2=(struct link *)malloc(sizeof(struct link));
    poly=(struct link *)malloc(sizeof(struct link));
    printf("\nenter 1st polynomial:");
    create(poly1);
    printf("\nenter 2nd polynomial:");
    create(poly2);
    printf("\n1st Number:");
    show(poly1);
    printf("\n2nd Number:");
    show(poly2);
    polyadd(poly1,poly2,poly);
    printf("\nAdded polynomial:");
    show(poly);
    printf("\n add two more numbers:");
		fflush(stdin);
scanf("%c",&ch);
    }
    while(ch=='y' || ch=='Y');
    }