Merge pull request #716 from KingArthur0205/remote

添加 二叉树的递归遍历.md C语言版本

problems/二叉树的递归遍历.md

@@ -360,8 +360,56 @@ var postorderTraversal = function(root) {
 };
 ```
 
+C:
+```c
+//前序遍历：
+void preOrderTraversal(struct TreeNode* root, int* ret, int* returnSize) {
+    if(root == NULL)
+        return;
+    ret[(*returnSize)++] = root->val;
+    preOrderTraverse(root->left, ret, returnSize);
+    preOrderTraverse(root->right, ret, returnSize);
+}
 
+int* preorderTraversal(struct TreeNode* root, int* returnSize){
+    int* ret = (int*)malloc(sizeof(int) * 100);
+    *returnSize = 0;
+    preOrderTraversal(root, ret, returnSize);
+    return ret;
+}
 
+//中序遍历：
+void inOrder(struct TreeNode* node, int* ret, int* returnSize) {
+    if(!node)
+        return;
+    inOrder(node->left, ret, returnSize);
+    ret[(*returnSize)++] = node->val;
+    inOrder(node->right, ret, returnSize);
+}
+
+int* inorderTraversal(struct TreeNode* root, int* returnSize){
+    int* ret = (int*)malloc(sizeof(int) * 100);
+    *returnSize = 0;
+    inOrder(root, ret, returnSize);
+    return ret;
+}
+
+//后序遍历：
+void postOrder(struct TreeNode* node, int* ret, int* returnSize) {
+    if(node == NULL) 
+        return;
+    postOrder(node->left, ret, returnSize);
+    postOrder(node->right, ret, returnSize);
+    ret[(*returnSize)++] = node->val;
+}
+
+int* postorderTraversal(struct TreeNode* root, int* returnSize){
+    int* ret= (int*)malloc(sizeof(int) * 100);
+    *returnSize = 0;
+    postOrder(root, ret, returnSize);
+    return ret;
+}
+```
 
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 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)