exercism/c/binary/binary.c

#include "binary.h"
#include <stdio.h>

int convert(const char *input) {
  int res = 0;
  for (size_t i = 0; input[i]; ++i) {
    if (input[i] != '0' && input[i] != '1') {
      res = INVALID;
      break;
    }
    res = res * 2 + (input[i] - '0');
  }
  return res;
}