#include <stdio.h>
#include <ctype.h>

int strToInt(const char *text)
{
  int n = 0, sign = 1;
  switch (*text) {
    case '-': sign = -1;
    case '+': ++text;
  }
  for (; isdigit(*text); ++text) n *= 10, n += *text - '0';
  return n * sign;
}

int main()
{
  const char *samples[] = {
    "123", "-234", "+345", "abc", ""
  };
  enum { n = sizeof samples / sizeof *samples };
  for (int i = 0; i < n; ++i) {
    printf("strToInt(\"%s\"): %d\n", samples[i], strToInt(samples[i]));
  }
  return 0;
}