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Binary tree right side view
Signed-off-by: Leo Ma <begeekmyfriend@gmail.com>
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‎199_binary_tree_right_side_view/Makefile

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all:
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gcc -O2 -o test bst_right.c

‎199_binary_tree_right_side_view/bst_right.c

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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#define BST_MAX_LEVEL 800
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#define container_of(ptr, type, member) \
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((type *)((char *)(ptr) - (size_t)&(((type *)0)->member)))
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#define list_entry(ptr, type, member) \
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container_of(ptr, type, member)
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#define list_first_entry(ptr, type, field) list_entry((ptr)->next, type, field)
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#define list_last_entry(ptr, type, field) list_entry((ptr)->prev, type, field)
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#define list_for_each(p, head) \
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for (p = (head)->prev; p != (head); p = p->prev)
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#define list_for_each_safe(p, n, head) \
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for (p = (head)->prev, n = p->prev; p != (head); p = n, n = p->prev)
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struct TreeNode {
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int val;
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struct TreeNode *left;
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struct TreeNode *right;
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};
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struct list_head {
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struct list_head *next, *prev;
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};
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static inline void INIT_LIST_HEAD(struct list_head *list)
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{
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list->next = list->prev = list;
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}
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static inline int list_empty(const struct list_head *head)
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{
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return (head->next == head);
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}
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static inline void __list_add(struct list_head *new, struct list_head *prev, struct list_head *next)
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{
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next->prev = new;
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new->next = next;
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new->prev = prev;
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prev->next = new;
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}
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static inline void list_add(struct list_head *_new, struct list_head *head)
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{
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__list_add(_new, head, head->next);
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}
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static inline void list_add_tail(struct list_head *_new, struct list_head *head)
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{
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__list_add(_new, head->prev, head);
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}
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static inline void __list_del(struct list_head *entry)
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{
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entry->next->prev = entry->prev;
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entry->prev->next = entry->next;
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}
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static inline void list_del(struct list_head *entry)
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{
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__list_del(entry);
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entry->next = entry->prev = NULL;
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}
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struct bfs_node {
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struct TreeNode *node;
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struct list_head link;
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};
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static struct bfs_node *node_new(struct list_head *free_list, struct TreeNode *node)
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{
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struct bfs_node *new;
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if (list_empty(free_list)) {
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new = malloc(sizeof(*new));
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} else {
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new = list_first_entry(free_list, struct bfs_node, link);
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list_del(&new->link);
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}
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new->node = node;
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return new;
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}
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static void queue(struct list_head *parents, struct list_head *children,
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struct list_head *free_list, int *results, int *count)
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{
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struct list_head *p, *n;
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list_for_each(p, parents) {
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struct bfs_node *new;
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struct bfs_node *parent = list_entry(p, struct bfs_node, link);
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if (parent->node->right != NULL) {
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new = node_new(free_list, parent->node->right);
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list_add(&new->link, children);
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}
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if (parent->node->left != NULL) {
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new = node_new(free_list, parent->node->left);
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list_add(&new->link, children);
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}
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}
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int first = 1;
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list_for_each_safe(p, n, parents) {
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struct bfs_node *parent = list_entry(p, struct bfs_node, link);
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if (first) {
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first = 0;
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results[(*count)++] = parent->node->val;
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}
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list_del(p);
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list_add(p, free_list);
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}
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}
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/**
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** Return an array of arrays of size *returnSize.
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** The sizes of the arrays are returned as *columnSizes array.
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** Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
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**/
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static int* rightSideView(struct TreeNode* root, int* returnSize)
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{
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if (root == NULL) {
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*returnSize = 0;
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return NULL;
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}
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struct list_head q0;
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struct list_head q1;
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struct list_head free_list;
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INIT_LIST_HEAD(&q0);
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INIT_LIST_HEAD(&q1);
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INIT_LIST_HEAD(&free_list);
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int level = 0;
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*returnSize = 0;
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int *results = malloc(BST_MAX_LEVEL * sizeof(int));
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struct bfs_node *new = node_new(&free_list, root);
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list_add_tail(&new->link, &q0);
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while (!list_empty(&q0) || !list_empty(&q1)) {
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if (level & 0x1) {
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queue(&q1, &q0, &free_list, results, returnSize);
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} else {
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queue(&q0, &q1, &free_list, results, returnSize);
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}
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level++;
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}
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return results;
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}
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int main(void)
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{
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struct TreeNode root;
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root.val = 3;
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struct TreeNode node1[2];
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node1[0].val = 9;
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node1[1].val = 20;
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struct TreeNode node2[4];
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node2[2].val = 15;
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//node2[3].val = 7;
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root.left = &node1[0];
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root.right = &node1[1];
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node1[0].left = NULL;
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node1[0].right = NULL;
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node1[1].left = &node2[2];
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node1[1].right = NULL;//&node2[3];
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node2[0].left = NULL;
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node2[0].right = NULL;
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node2[1].left = NULL;
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node2[1].right = NULL;
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node2[2].left = NULL;
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node2[2].right = NULL;
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node2[3].left = NULL;
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node2[3].right = NULL;
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int i, count = 0;
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int *lists = rightSideView(&root, &count);
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for (i = 0; i < count; i++) {
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printf("%d ", lists[i]);
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}
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printf("\n");
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return 0;
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}

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