How do I convert a binary string like "010011101" to an int, and how do I convert an int, like 5, to a string "101" in C?
The strtol
function in the standard library takes a "base" parameter, which in this case would be 2.
int fromBinary(char *s) {
return (int) strtol(s, null, 2);
}
(first C code I've written in about 8 years :-)
I guess it really depends on some questions about your strings/program. If, for example, you knew your number wouldn't be bigger than 255 (IE you were only using 8 bits or 8 0s/1s), you could create a function where you hand it 8 bits from your string, traverse it and add to a sum that you returned everytime you hit a 1. IE if you hit the bit for 2^7 add 128 and the next bit you hit was 2^4 add 16.
This is my quick and dirty idea. I think more and Google for ya while at school. :D
If it is a homework problem they probably want you to implement strtol
, you would have a loop something like this:
char* start = &binaryCharArray[0];
int total = 0;
while (*start)
{
total *= 2;
if (*start++ == '1') total += 1;
}
If you wanted to get fancy you could use these in the loop:
total <<= 1;
if (*start++ == '1') total^=1;
For the 2nd part of the question, i.e. "how do I convert an int, like 5, to a string "101" in C?", try something like:
void
ltostr( unsigned long x, char * s, size_t n )
{
assert( s );
assert( n > 0 );
memset( s, 0, n );
int pos = n - 2;
while( x && (pos >= 0) )
{
s[ pos-- ] = (x & 0x1) ? '1' : '0'; // Check LSb of x
x >>= 1;
}
}
Dear Friend,
You can use the following coding
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main (void)
{
int nRC = 0;
int nCurVal = 1;
int sum = 0;
char inputArray[9];
memset(inputArray,0,9);
scanf("%s", inputArray);
// now walk the array:
int nPos = strlen(inputArray)-1;
while(nPos >= 0)
{
if( inputArray[nPos] == '1')
{
sum += nCurVal;
}
--nPos;
nCurVal *= 2;
}
printf( "%s converted to decimal is %d\n", inputArray, sum);
return nRC;
}