1 files changed, 53 insertions, 0 deletions
diff --git a/4/12.c b/4/12.c
new file mode 100644
index 0000000..9d5a0e2
--- /dev/null
+++ b/4/12.c
@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define MAXLEN 100
+
+void mitoa(int, char[]);
+int mgetline(char[], int);
+
+int main() {
+  int n;
+  char s1[MAXLEN], s2[MAXLEN];
+
+  while (mgetline(s1, MAXLEN)) {
+    n = atoi(s1);
+    memset(s2, 0, sizeof(s2));
+    mitoa(n, s2);
+    printf("\t%s\n", s2);
+  }
+
+  return 0;
+}
+
+int step = 0;
+
+void mitoa(int n, char s[]) {
+  if (step >= MAXLEN - 1) {
+    s[MAXLEN - 1] = 0;
+    printf("error: number too large.\n");
+    return;
+  }
+
+  if (n < 0) {
+    s[step++] = '-';
+    n = -n;
+  }
+
+  if (n / 10)
+    mitoa(n / 10, s);
+  s[step++] = n % 10 + '0';
+}
+
+int mgetline(char s[], int max) {
+  int c, i;
+
+  step = 0;
+  
+  for (i = 0; i < max - 1 && (c = getchar()) != '\n' && c != EOF; i++)
+    s[i] = c;
+  s[i] = 0;
+  
+  return c != '\n' && c != EOF ? -1 : i - 1;
+}