C-将二进制转换为十进制的算法-不起作用

Question

#include <stdio.h>
#include <stdlib.h>

int main()
{
char c1,c2,c3,c4,c5;
int x;

scanf(" %c %c %c %c %c",&c1,&c2,&c3,&c4,&c5);

if (c1,c2,c3,c4,c5 !='0' && c1,c2,c3,c4,c5 !='1'){
    printf("Not a binary number!");

    }

if (c1=='0' && c2,c3,c4,c5=='0' || c2,c3,c4,c5 =='1'){

    c5 = c5-48;
    c4 = (c4-48)*2;
    c3 = (c3-48)*4;
    c2 = (c2-48)*8;
    c1 = c1-48;

    x = c5+c4+c3+c2+c1;
    printf("%d",x);
    }

return 0;
}

So the code works for all numbers except when there's a 0(zero) typed as last(c5) character. When that happens I get "Not a binary number!". Where is my mistake? :)

I'm only getting started into C and programming so be kind with me heheh

Answer 1

first you cant take the binary digits at once, you have c1 to c5, what if the user enter the binary for 100, it will not work. so try something like this. Try out this:

#include <stdio.h>
#include <stdlib.h>

int main()
{

int val, base = 1,cn, decinum = 0,rest;
int alert = 0;
printf("Please enter a binary number 0's and 1's: ");

scanf("%d",&val);

cn = val;   // saving it for printf
while(val > 0){
    rest = val % 10;

    if(rest == 0 || rest == 1) {
        decinum += rest * base;
        val /= 10;
        base *= 2;

    }else{
        alert = 1;
        break;
    }
}


if(alert){
    printf("Sorry not a binary number\n");
}else{
    printf("binary: %d ist %d",cn,decinum);
}


return 0;
}

Please enter a binary number 0's and 1's: 01120100

output: Sorry not a binary number

Please enter a binary number 0's and 1's: 101

Output: binary: 101 ist 5

From the comments from cpatricio and Jonathan, you have large number for binary in mind like 8bits, and maximum 20 bits

int main()
{

unsigned long  val,cn, decinum = 0;
int rest, base = 1;
int alert = 0;
printf("Please enter a binary number 0's and 1's: ");

scanf("%lu",&val);

cn = val;  // save it for printf otherwise after the while loop is val = 0

while(val > 0){
    rest = val % 10;

    if(rest == 0 || rest == 1) {
        decinum += rest * base;
        val /= 10;
        base *= 2;

    }else{
        alert = 1;
        break;
    }
}


if(alert){
    printf("Sorry not a binary number\n");
}else{
    printf("binary: %lu ist %ld",cn,decinum);
}


return 0;
}

probe Output: Please enter a binary number 0's and 1's:010101100001001011000 binary: 010101100001001011000 ist 705112

Output: Please enter a binary number 0's and 1's:0000001001011000 binary: 0000001001011000 ist 600