feat(tree): add C codes

codes/c/chapter_tree/binary_tree_dfs.c

@@ -0,0 +1,72 @@
+/**
+ * File: binary_tree_dfs.c
+ * Created Time: 2023-01-11
+ * Author: Reanon (793584285@qq.com)
+ */
+
+#include "../include/include.h"
+
+/* 辅助数组，用于存储遍历序列 */
+int *arr;
+
+/* 前序遍历 */
+void preOrder(TreeNode *root, int *size) {
+
+    if (root == NULL) return;
+    // 访问优先级：根结点 -> 左子树 -> 右子树
+    arr[(*size)++] = root->val;
+    preOrder(root->left, size);
+    preOrder(root->right, size);
+}
+
+/* 中序遍历 */
+void inOrder(TreeNode *root, int *size) {
+    if (root == NULL) return;
+    // 访问优先级：左子树 -> 根结点 -> 右子树
+    inOrder(root->left, size);
+    arr[(*size)++] = root->val;
+    inOrder(root->right, size);
+}
+
+/* 后序遍历 */
+void postOrder(TreeNode *root, int *size) {
+    if (root == NULL) return;
+    // 访问优先级：左子树 -> 右子树 -> 根结点
+    postOrder(root->left, size);
+    postOrder(root->right, size);
+    arr[(*size)++] = root->val;
+}
+
+
+/* Driver Code */
+int main() {
+    /* 初始化二叉树 */
+    // 这里借助了一个从数组直接生成二叉树的函数
+    int nums[] = {1, 2, 3, 4, 5, 6, 7};
+    int size = sizeof(nums) / sizt ceof(int);
+    TreeNode *root = ArrayToTree(nums, size);
+    printf("初始化二叉树\n");
+    PrintTree(root);
+
+    /* 前序遍历 */
+    // 初始化辅助数组
+    arr = (int *) malloc(sizeof(int) * MAX_NODE_SIZE);
+    size = 0;
+    preOrder(root, &size);
+    printf("前序遍历的结点打印序列 = ");
+    PrintArray(arr, size);
+
+    /* 中序遍历 */
+    size = 0;
+    inOrder(root, &size);
+    printf("中序遍历的结点打印序列 = ");
+    PrintArray(arr, size);
+
+    /* 后序遍历 */
+    size = 0;
+    postOrder(root, &size);
+    printf("后序遍历的结点打印序列 = ");
+    PrintArray(arr, size);
+
+    return 0;
+}