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// 590. N-ary Tree Postorder Traversal
#include "leetcode.h"
/*
* given the 'root' of an n-ary tree, return the postorder traversal of its
* nodes' values. nary-tree input serialisation is represented in their level
* order traversal. each group of children is separated by the null value.
*/
void *post_vis(struct Node *root, int *n, int *idx) {
int i = 0, cnt[1000] = {0};
struct Node *prev[1000];
prev[i++] = NULL;
while (root) {
if (root->numChildren == cnt[i]) {
n[(*idx)++] = root->val;
cnt[i--] = 0;
root = prev[i];
} else {
prev[i] = root;
root = root->children[cnt[i++]++];
}
}
return NULL;
}
int *postorder(struct Node *root, int *returnSize) {
int *n = (int *)calloc(10000, sizeof(int)), idx = 0;
post_vis(root, n, &idx);
*returnSize = idx;
return n;
}
int main() {
struct Node *root = node_create(1, 3);
root->children[0] = node_create(3, 2);
root->children[1] = node_create(2, 0);
root->children[2] = node_create(4, 0);
root->children[0]->children[0] = node_create(5, 0);
root->children[0]->children[1] = node_create(6, 0);
int rs, *p = postorder(root, &rs);
for (int i = 0; i < rs; i++)
printf("%d ", p[i]); // expect: 5 6 3 2 4 1
free(p);
}
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