[c语言算法]二叉树中序遍历

递归法

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
    int inorder(struct TreeNode *root,int *arrRet,int *returnSize){
        if(root){
            inorder(root->left,arrRet,returnSize);
            arrRet[(*returnSize)++] = root->val;
            inorder(root->right,arrRet,returnSize);
        }
        return 0;
} 

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* inorderTraversal(struct TreeNode* root, int* returnSize){
    int *arrRet = (int*)malloc(sizeof(int)*200);
    *returnSize = 0;
    inorder(root,arrRet,returnSize);
    return arrRet;
}

非递归