first commit!

atoi_v2.c

@@ -0,0 +1,27 @@
+#include <ctype.h>
+#include <stdio.h>
+
+int atoi(char string[]) {
+  int i, sign_ext, res;
+
+  for (i = 0; isspace(string[i]); ++i)
+    ;
+
+  sign_ext = string[i] == '-' ? -1 : 1;
+  if (string[i] == '-')
+    ++i;
+
+  for (res = 0; isdigit(string[i]); ++i) {
+    res = res * 10 + (string[i] - '0');
+  }
+
+  return sign_ext * res;
+}
+
+int main() {
+  printf("%d\n", atoi("123"));
+  printf("%d\n", atoi("-123"));
+  printf("%d\n", atoi("+123"));
+  printf("%d\n", atoi("0123"));
+  printf("%d\n", atoi("0123.1"));
+}