refactor(structure): normalize folder names with leading zeros for consistency

- Renamed all folders from format NEx (e.g., 1Ex, 2Ex...) to 0NEx (01Ex, 02Ex, etc.)
- Updated subdirectories and files accordingly
- Removed old main Makefile and tasks (a01.c–a09.c, solve.c, io_status.h), likely obsolete
- Cleaned up deprecated task binaries and configs

2025.02.28/06Ex/solve.c

@@ -0,0 +1,21 @@
+#include "solve.h"
+
+void t6_solve(char **a, int n, int (*cmp)(const char *, const char *))
+{
+	int i;
+	for (i = 1; i < n; ++i)	append(a, i+1, a[i], find(a, i, a[i], cmp));
+}
+
+int find(char **arr, int n, char *a, int (*cmp)(const char *, const char *))
+{
+	int i;
+	for (i=0; i<n; ++i) if (cmp(a, arr[i]) < 0) break;
+	return i;
+}
+
+void append(char **arr, int n, char *a, int index)
+{
+	for (int i = n-1; i > index; --i) arr[i] = arr[i-1];
+	arr[index] = a;
+}
+