Simplify struct declarations of C.

Use PascalCase for all structs in C.
SImplify n_queens.c
Format C code for chapter of graph.

codes/c/utils/list_node.h

@@ -12,13 +12,10 @@ extern "C" {
 #endif
 
 /* 链表节点结构体 */
-struct ListNode {
+typedef struct ListNode {
     int val;               // 节点值
     struct ListNode *next; // 指向下一节点的引用
-};
-
-// typedef 作用是为一种数据类型定义一个新名字
-typedef struct ListNode ListNode;
+} ListNode;
 
 /* 构造函数，初始化一个新节点 */
 ListNode *newListNode(int val) {
@@ -56,4 +53,4 @@ ListNode *getListNode(ListNode *head, int val) {
 }
 #endif
 
-#endif // LIST_NODE_H
+#endif // LIST_NODE_H

codes/c/utils/print_util.h

@@ -72,12 +72,10 @@ static void printLinkedList(ListNode *node) {
     printf("%d\n", node->val);
 }
 
-struct Trunk {
+typedef struct Trunk {
     struct Trunk *prev;
     char *str;
-};
-
-typedef struct Trunk Trunk;
+} Trunk;
 
 Trunk *newTrunk(Trunk *prev, char *str) {
     Trunk *trunk = (Trunk *)malloc(sizeof(Trunk));

codes/c/utils/tree_node.h

@@ -16,14 +16,12 @@ extern "C" {
 #define MAX_NODE_SIZE 5000
 
 /* 二叉树节点结构体 */
-struct TreeNode {
+typedef struct TreeNode {
     int val;                // 节点值
     int height;             // 节点高度
     struct TreeNode *left;  // 左子节点指针
     struct TreeNode *right; // 右子节点指针
-};
-
-typedef struct TreeNode TreeNode;
+} TreeNode;
 
 TreeNode *newTreeNode(int val) {
     TreeNode *node;