Binary addition using char array

Question

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <stdio.h>


int main(){

    char Pbuf8[9]={"01100000"};
    char Mbuf4[10]={"01110000"};

    int num=0;
    char Snum[9]="0";   
    int carry=0;


    for(int c=7;c>=0;c--){

        //Convert a string to a number and add
        num=(Pbuf8[c]-'0')+(Mbuf4[c]-'0')+carry;

        //binary addition
        if(num==1){
            Snum[c]=num;
            carry=0;
        }else if(num==2){
            num=0;
            carry=1;
            Snum[c]=num;
        }else if(num==3){
            num=1;
            carry=1;
            Snum[c]=num;
        }
        //Convert num to string and store in Snum
        sprintf(Snum, "%d", num);  
    }
    //output
    printf("%s",Snum);
     

    return 0;
}

Calculate and output the sum of Pbuf8 and Mbuf4.

I want to output '00001011' but '1' is output.

If there is no 'sprintf(number, "%d", number);' does not exist, 'rr' is output.

How do I get the value I want?

Answer 1

You have 3 minor bugs in your code.

• Snum must be initialized with everything being 0. Otherwise it will just be filled with one 0 and the lower part of the addition will not be visible
• You need to convert "num" back to a number, before adding it back to the char array. So, num+'0'
• Delete the "sprintf", It will overwrite the previously created result.

The corrected code will look like:

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <stdio.h>


int main(){

    char Pbuf8[9]={"01100000"};
    char Mbuf4[10]={"01110000"};

    int num=0;
    char Snum[9]="00000000";   
    int carry=0;


    for(int c=7;c>=0;c--){

        //Convert a string to a number and add
        num=(Pbuf8[c]-'0')+(Mbuf4[c]-'0')+carry;

        //binary addition
        if(num==1){
            Snum[c]=num+'0';
            carry=0;
        }else if(num==2){
            num=0;
            carry=1;
            Snum[c]=num+'0';
        }else if(num==3){
            num=1;
            carry=1;
            Snum[c]=num+'0';
        }
        //Convert num to string and store in Snum
        //sprintf(Snum, "%d", num);  
    }
    //output
    printf("%s",Snum);
     

    return 0;
}