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145.binary-tree-postorder-traversal.c
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145.binary-tree-postorder-traversal.c
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/*
* @lc app=leetcode id=145 lang=c
*
* [145] Binary Tree Postorder Traversal
*/
#include "include/type.h"
// @lc code=start
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/
/**
* Note: The returned array must be malloced, assume caller calls free().
*/
#include <stdlib.h>
int *postorderTraversal(struct TreeNode *root, int *returnSize)
{
if (root == NULL)
{
*returnSize = 0;
return NULL;
}
if (root->left == NULL && root->right == NULL)
{
*returnSize = 1;
int *traversal = (int *)malloc(sizeof(int));
traversal[0] = root->val;
return traversal;
}
*returnSize = 0;
int *traversal = (int *)malloc(sizeof(int) * 100);
struct TreeNode **trace = (struct TreeNode **)malloc(sizeof(struct TreeNode *) * 100);
int trace_idx = 0;
trace[trace_idx] = root;
while (trace_idx >= 0)
{
struct TreeNode *cur = trace[trace_idx];
if (cur->left != NULL)
{
trace[++trace_idx] = cur->left;
cur->left = NULL;
}
else if (cur->right != NULL)
{
trace[++trace_idx] = cur->right;
cur->right = NULL;
}
else
{
traversal[(*returnSize)++] = trace[trace_idx--]->val;
}
}
return traversal;
}
// @lc code=end
int main(int argc, char const *argv[])
{
struct TreeNode *root = (struct TreeNode *)malloc(sizeof(struct TreeNode));
root->val = 1;
root->left = NULL;
root->right = (struct TreeNode *)malloc(sizeof(struct TreeNode));
root->right->val = 2;
root->right->left = (struct TreeNode *)malloc(sizeof(struct TreeNode));
root->right->right = NULL;
root->right->left->val = 3;
root->right->left->left = NULL;
root->right->left->right = NULL;
int *returnSize = (int *)malloc(sizeof(int));
postorderTraversal(root, returnSize);
return 0;
}