division_using_string.cpp

/*
  Author : Abhishek Yadav
  Roll NO: CS12B032
   
    this programs calculates the quotient of a division upto nth places of decimal
    So as a part of input you have to enter first numerator which can be anything(fraction, some invalid string
    , which, after validation check will be rejected), and second input as denominator and third is the number of places
    after decimal you want to print the result.  
*/




#include<iostream>
#include<cmath>
using namespace std;
#include"double_linked_list.cpp"

void divide(string &str1,string &str2,unsigned long long n)
{ 
    int flag1=0,flag2=0,i=0,j=0;
    if(str1[0]=='-'){
        flag1++; i++;
      }
      if(str2[0]=='-'){
          flag2++;j++;
      }
    //counts how many digits are there in numerator after decimal
    int count_after_decimal_num=0;
    //counts digits after decimal in denominator
    int count_after_decimal_denom=0;
    int decimal_flag=0,k=0;
    int l1=str1.length();
     int temp=l1;
    l1--;
   
    unsigned long long num=0;
    unsigned long long denom=0;
    while(l1>=i){
        if(isdigit(str1[l1])) 
             num+=pow(10,k++)*(str1[l1]-'0');
         else decimal_flag++;
         if(decimal_flag) count_after_decimal_num++;
         l1--;
        }
        if(count_after_decimal_num){
          if(str1[0]!='-')
          count_after_decimal_num=temp-count_after_decimal_num;
          else count_after_decimal_num=temp-count_after_decimal_num-1;
          }
          
  // cout <<num << " "<<count_after_decimal_num<<endl;
    l1=str2.length();
    temp=l1;
    l1--;k=0;
    decimal_flag=0;
    while(l1>=j){
        if(isdigit(str2[l1])) 
             denom+=pow(10,k++)*(str2[l1]-'0');
         else decimal_flag++;
         if(decimal_flag) count_after_decimal_denom++;
         l1--;
        }
if(count_after_decimal_denom){
               if(str2[0]!='-')
          count_after_decimal_denom=temp-count_after_decimal_denom;
          else count_after_decimal_denom=temp-count_after_decimal_denom-1;
    //cout <<denom << " "<<count_after_decimal_denom<<endl;
   }
   if(denom==0){
   
   cout <<"infinity\n";
   return ;}
   else if(num==0){
   cout <<num <<endl;return;}
    if(num==denom){
          cout << num/denom <<" " <<endl;
          return;
      }
         
	temp=num;
	int temp_=denom;
	unsigned long long counter=0;
	int count_upto_decimal=0;
	int count_num=0;
	 list* div_list=NULL;
	
	
	 if(temp<temp_){
	     while(temp<temp_)
	     {
	        temp*=10;
	        count_num++;
	     }
	 }
	 if(temp>temp_){
	        int local=temp/temp_;
	       while(local>0){
	         div_list=add_list_in_reverse(div_list,local%10);
	           count_upto_decimal++;
	           local/=10;
	        }
	        temp%=temp_;
	     }
	    
             while(temp<temp_){
                if(counter==n|| temp==0)
                 break;
                   int flag=0;
                     while(temp<temp_){
                        temp*=10;
                        if(flag>=1)
                          div_list=add_node_in_list(div_list,0);
                     flag++;
                 }
                 div_list=add_node_in_list(div_list,temp/temp_);
                 temp%=temp_; 
                 counter++;
                 
	      }
	     
	      if(flag1^flag2)
	      cout <<"-";
	     int temp3= count_after_decimal_denom - count_after_decimal_num - count_num + count_upto_decimal;
	     // cout <<temp3  <<" " <<count_after_decimal_denom <<" "<<count_after_decimal_num
	      //<<" " << count_num <<" " <<count_upto_decimal <<endl;
	      if(temp3<0){
	      cout <<".";
	          while(temp3<0){
	          cout <<"0" ;
	          temp3+=1;
	          }
	           list *flag_list=div_list;
	      while(flag_list!=NULL){
	      cout <<flag_list->data;
	      flag_list=flag_list->rear;
	      }
	     
	   }else {
	      list *flag_list=div_list;
	      while(flag_list!=NULL){
	      if(temp3==0)
	      cout <<".";
	      cout <<flag_list->data;
	      flag_list=flag_list->rear;
	      --temp3;
	      }
	     
	   }
	      cout <<endl;
	      return ;
 }
 bool verify_num(string &str)
 {
    int l=str.length();
    int flag=0;
     int i=0;
     if(str[i]=='-')
     i++;
    while(i<l){
      if(isdigit(str[i])){i++;continue;}
         else if(str[i]=='.' && flag==0)
            flag++;
         else break;
        i++;
     }
     
     if(i<l) return false ;
     else return true;
     
 }
int main()
{
   string str1,str2;
    cout <<"enter Numerator : ";
    getline(cin,str1); 
    if(!verify_num(str1)){
    cout <<"Input not consistent:\n";
     return 0;
     }
    cout <<"Enter denominator: ";
    getline(cin,str2);
    if(!verify_num(str2)){
    cout <<"Input not consistent:\n";
     return 0;
     }
    
    cout <<"After Decimal, upto how many digits do you want the result:? \n";
    unsigned long long n;
    cin >>n; 
     cout <<"result of division is: \n";  
   divide(str1,str2,n);
   return 0;
}