add utility function replace_multiple_space_with_one()

use it to parse the interactive input

src/util.c

@@ -0,0 +1,38 @@
+#include <string.h>
+
+void replace_multiple_space_with_one(char *s)
+{
+    int j = 0;
+    int count = 0;
+    int len = strlen(s);
+
+    if (len == 1 && (s[0] == ' ' || s[0] == '\t'))
+    {
+        s[0] = '\0';
+        return;
+    }
+
+    if (len < 2)
+        return;
+
+    for (int i = 0; s[i] != '\0'; i++)
+    {
+        if (s[i] == ' ' || s[i] == '\t')
+        {
+            count++;
+        }
+
+        if (s[i] != ' ' && s[i] != '\t')
+        {
+            if (count >= 1)
+            {
+                count = 0;
+                s[j++] = ' ';
+            }
+            s[j++] = s[i];
+        }
+    }
+    s[j] = '\0';
+
+    return;
+}