leetcode 145 二叉树的后序遍历 C语言实现 非递归

题目

代码

int* postorderTraversal(struct TreeNode* root, int* returnSize){
    *returnSize = 0;
    if (root == NULL) return 0;
    #define MAX 1000000
    int *arr = (int *)malloc(sizeof(int) * MAX);
    struct TreeNode *stack[MAX], *p = root, *pre = NULL;//pre记录节点是从左边返回还是右边
    int top = -1;
    while (top >= 0 || p) {
        if (p) {
            stack[++top] = p;
            p = p->left;
        } else {
            p = stack[top];
            if (p->right != pre && p->right) p = p->right;
            else {
                arr[(*returnSize)++] = p->val;
                top--;
                pre = p;
                p = NULL;
            }
        }
    }
    return arr;
}

来源：CSDN

作者：瓶邪写一个夏天

链接：https://blog.csdn.net/qq_42007287/article/details/104590563