interviewstreet

changing_bits.cpp

#include<stdio.h>
#include<string.h>
#include<ctype.h>
void inline polyadd(unsigned short int A[],unsigned short int B[],unsigned short int C[], int);
void inline display(unsigned short int A[],int);
void inline polyset(unsigned short int A[],int,int);
int main()
{
      unsigned short int A[6250]={0};
      unsigned short int B[6250]={0};
      unsigned short int C[6251]={0};
      unsigned short int mask=0,mask1=0;
      int n=0,q=0;char c;int i=0,size=0,coun_i=0;
      scanf("%d%d",&n,&q);
      //Reading the initial value of A & B
      getchar();int a_c=0,a_r=0;
      while((c=getchar())!='\n')
      {
               if(c=='1'){
                       mask1=1;
                       mask1=mask1<<a_c;
                       mask=mask|mask1;
                       mask1=0;
               }
               if(isdigit(c))               
		a_c++;
               if(a_c==16){
                       A[a_r++]=mask;
                       mask=0;
                       a_c=0;
               }



      }
      if(a_c!=0){
                       A[a_r]=mask;

      }

      i=0;a_r=0,a_c=0,mask=0,mask1=0;
      while((c=getchar())!='\n')
      {
               if(c=='1'){
                       mask1=1;
                       mask1=mask1<<a_c;
                       mask=mask|mask1;
                       mask1=0;
               }
		if(isdigit(c))               
		a_c++;
               if(a_c==16){
                       B[a_r++]=mask;
                       mask=0;
                       a_c=0;
               }
      }
      if(a_c!=0){
                       B[a_r]=mask;

      }

   char input[10];
       int index=0;
       int set=0,r_c=0;

    coun_i=0;
    while(coun_i<q)
    {
              scanf("%s",input);
              if(!strcmp("set_a",input))
              {       scanf("%d%d",&index,&set);
                      polyset(A,index,set);
                      r_c=0;

              }
              else if(!strcmp("set_b",input))
              {        scanf("%d%d",&index,&set);
                       polyset(B,index,set);
                       r_c=0;
              }
              else if(!strcmp("get_c",input))
              {        scanf("%d",&index);
                       if(r_c==0){
				C={0};
                               polyadd(A,B,C,n);
			}
                       display(C,index);
                       r_c=1;
              }
              else
              {}
              coun_i++;
      }

      return 0;
}
void polyset(unsigned short int A[6250],int index,int set)
{
       unsigned short a=0,b=0,c=0,d=0,f=0,set1=1,set2=65535;
       a=index/16; b=index%16; c=set;d=c<<b;
       f=A[a]&(set1<<b);
       if(!set)
          set2=set2^(set1<<b);
       if(f)
          A[a]=A[a]&set2;
       else
          A[a]=A[a]|d;
}

void polyadd(unsigned short int A[6250],unsigned short int B[6250],unsigned short int C[6251],int s)
{      unsigned int carry=0,i=0;
      int a=s/16+1;
      if(a>6250) a--;
      for(i=0;i<a;i++)
      {
              C[i]=(A[i]+B[i]+carry)%65536;
              carry=(A[i]+B[i]+carry)/65536;
      }
      if(carry && i==6250)
         C[i]=carry;

}


void display(unsigned short int A[6251],int index)
{      int a=0,b=0,c=0,d=0,f=0,set=1,k=0;
       a=index/16; b=index%16; c=set;d=c<<b;
	k=A[a];       
	f=k&d;
       if(f)
          printf("%d",1);
       else
          printf("%d",0);

}

This is the solution for the puzzle "Changing Bits" from the interviewstreet. The code is not optimized. Please suggest what should be the approach for the same.

The above code is failing for some 4 hidden test cases....could some body has any idea what could be it.