diff --git a/ch_03/exercise_03-03/main.c b/ch_03/exercise_03-03/main.c
new file mode 100644
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--- /dev/null
+++ b/ch_03/exercise_03-03/main.c
@@ -0,0 +1,118 @@
+/*
+ *
+ * Exercise 3-3. Write a function expand(s1,s2) that expands shorthand
+ * notations like a-z in the string s1 into the equivalent complete
+ * list abc...xyz in s2. Allow for letters of either case and digits,
+ * and be prepared to handle cases like a-b-c and a-z0-9 and -a-z.
+ * Arrange that leading or trailing - is taken literally
+ *
+ *
+ * Author: Kun Deng
+ */
+
+#include <stdio.h>
+
+#define ARRAY_SIZE 1024
+
+
+// If the characters are of the same type and
+// if s is less than t, then the characters can
+// be expanded.
+// Returns 1 if expandable
+int can_expand(char s, char t);
+
+// Expands shorthand notations like a-z in the string s1 into
+// the equivalent complete list abc...xyz in s2. The result will
+// be stored in string s2
+void expand(char *s1, char *s2);
+
+
+int main()
+{
+    char *s1 = "safeaf3-934bd-b-p0A-Fs0-9-Zaae-f-gsa";
+    char s2[ARRAY_SIZE];
+
+    printf("Before expand\n%s\n\n", s1);
+    expand(s1, s2);
+    printf("After expand\n%s\n", s2);
+
+    return 0;
+}
+
+
+int can_expand(char s, char t)
+{
+    int result = 0;
+
+    if ((48 <= s && s <= 57) && (48 <= t && t <= 57))
+    {
+        // Both characters are numbers
+        if (s < t)
+        {
+            // printf("%c (%d) and %c (%d) are numbers\n", s, s, t, t);
+            // Can be expanded
+            result = 1;
+        }
+    }
+    else if ((65 <= s && s <= 90) && (65 <= t && t <= 90))
+    {
+        // Both characters are uppercase characters
+        if (s < t)
+        {
+            // printf("%c and %c are uppercase letters\n", s, t);
+            // Can be expanded
+            result = 1;
+        }
+    }
+    else if ((97 <= s && s <= 122) && (97 <= t && t <= 122))
+    {
+        // Both characters are lowercase characters
+        if (s < t)
+        {
+            // Can be expanded
+            result = 1;
+        }
+    }
+
+    return result;
+}
+
+
+void expand(char *s1, char *s2)
+{
+    int i, j;
+    for (i = 0, j = 0; s1[i] != '\0'; ++i)
+    {
+        if (s1[i] == '-' && s1[(i + 1)] != '\0' && i != 0 && s1[(i - 1)] != '-' && s1[(i + 1)] != '-')
+        {
+            char a1 = s1[(i - 1)];
+            char a2 = s1[(i + 1)];
+
+            if (can_expand(a1, a2) == 1)
+            {
+                // printf("Can expand %c (%d) and %c (%d)\n", a1, a1, a2, a2);
+
+                for (int k = (a1 + 1); k < a2; ++k)
+                {
+                    char c = k;
+
+                    // printf("%c %d\n", c, k);
+
+                    s2[j++] = c;
+                }
+            }
+            else
+            {
+                // printf("Can't expand %c (%d) and %c (%d)\n", a1, a1, a2, a2);
+                s2[j++] = s1[i];
+            }
+        }
+        else
+        {
+            // printf("Regular letter %c\n", s1[i]);
+            s2[j++] = s1[i];
+        }
+    }
+
+    s2[j] = '\0';
+}