修改目录结构，优化CMakeLists

src/144.c

@@ -0,0 +1,43 @@
+#include "include/TreeNode.h"
+#include <stdlib.h>
+
+struct list_t
+{
+    int *data;
+    size_t size;
+};
+
+void append(struct list_t *self, int v)
+{
+    if (!self->data)
+        self->data = (int *)malloc(sizeof(int));
+    else
+        self->data = (int *)realloc(self->data, (self->size + 1) * sizeof(int));
+
+    self->data[self->size - 1] = v;
+    self->size += 1;
+}
+
+void preorder(struct TreeNode *root, struct list_t *list)
+{
+    if (!root)
+        return;
+    append(list, root->val);
+    preorder(root->left, list);
+    preorder(root->right, list);
+}
+
+int *preorderTraversal(struct TreeNode *root, int *returnSize)
+{
+    struct list_t l = {NULL, 0};
+
+    preorder(root, &l);
+
+    *returnSize = l.size;
+    return l.data;
+}
+
+int main()
+{
+    return 0;
+}