Construct binary tree from order traversal

Signed-off-by: Leo Ma <[email protected]>

105_construct_binary_tree_from_preorder_and_inorder_traversal/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test binary_tree_build.c

105_construct_binary_tree_from_preorder_and_inorder_traversal/binary_tree_build.c

@@ -0,0 +1,199 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct hlist_node;
+
+struct hlist_head {
+    struct hlist_node *first;
+};
+
+struct hlist_node {
+    struct hlist_node *next, **pprev;
+};
+
+static inline void INIT_HLIST_HEAD(struct hlist_head *h) {
+    h->first = NULL;
+}
+
+static inline void INIT_HLIST_NODE(struct hlist_node *n) {
+    n->next = NULL;
+    n->pprev = NULL;
+}
+
+static inline int hlist_empty(struct hlist_head *h) {
+    return !h->first;
+}
+
+static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
+{
+    if (h->first != NULL) {
+        h->first->pprev = &n->next;
+    }
+    n->next = h->first;
+    n->pprev = &h->first;
+    h->first = n;
+}
+
+static inline void hlist_del(struct hlist_node *n)
+{
+    struct hlist_node *next = n->next;
+    struct hlist_node **pprev = n->pprev;
+    *pprev = next;
+    if (next != NULL) {
+        next->pprev = pprev;
+    }
+}
+
+#define container_of(ptr, type, member) \
+    ((type *)((char *)(ptr) - (size_t)&(((type *)0)->member)))
+
+#define list_entry(ptr, type, member) \
+    container_of(ptr, type, member)
+
+#define hlist_for_each(pos, head) \
+    for (pos = (head)->first; pos; pos = pos->next)
+
+struct TreeNode {
+    int val;
+    struct TreeNode *left;
+    struct TreeNode *right;
+};
+
+struct order_node {
+    struct hlist_node node;
+    int val;
+    int index;
+};
+
+static int find(int num, int size, struct hlist_head *heads)
+{
+    struct hlist_node *p;
+    int hash = (num < 0 ? -num : num) % size;
+    hlist_for_each(p, &heads[hash]) {
+        struct order_node *on = list_entry(p, struct order_node, node);
+        if (num == on->val) {
+            return on->index;
+        }
+    }
+    return -1;
+}
+
+static struct TreeNode *node_new(int val)
+{
+    struct TreeNode *tn = malloc(sizeof(*tn));
+    tn->val = val;
+    tn->left = NULL;
+    tn->right = NULL;
+    return tn;
+}
+
+static struct TreeNode *recursive(int *preorder, int pre_low, int pre_high,
+                                  int *inorder, int in_low, int in_high,
+                                  struct hlist_head *in_heads, int size)
+{
+    if (in_low > in_high || pre_low > pre_high) {
+        return NULL;
+    }
+    struct TreeNode *tn = malloc(sizeof(*tn));
+    tn->val = preorder[pre_low];
+    int index = find(preorder[pre_low], size, in_heads);
+    tn->left = recursive(preorder, pre_low + 1, pre_low + (index - in_low), inorder, in_low, index - 1, in_heads, size);
+    tn->right = recursive(preorder, pre_high - (in_high - index - 1), pre_high, inorder, index + 1, in_high, in_heads, size);
+    return tn;
+}
+
+static void node_add(int val, int index, int size, struct hlist_head *heads)
+{
+    struct order_node *on = malloc(sizeof(*on));
+    on->val = val;
+    on->index = index;
+    int hash = (val < 0 ? -val : val) % size;
+    hlist_add_head(&on->node, &heads[hash]);
+}
+
+static struct TreeNode *buildTree(int *preorder, int preorderSize, int *inorder, int inorderSize)
+{
+    int i, j;
+    struct hlist_head *in_heads = malloc(inorderSize * sizeof(*in_heads));
+    for (i = 0; i < inorderSize; i++) {
+        INIT_HLIST_HEAD(&in_heads[i]);
+    }
+    for (i = 0; i < inorderSize; i++) {
+        node_add(inorder[i], i, inorderSize, in_heads);
+    }
+
+#if 0
+    struct hlist_head *pre_heads = malloc(preorderSize * sizeof(*pre_heads));
+    for (i = 0; i < preorderSize; i++) {
+        INIT_HLIST_HEAD(&pre_heads[i]);
+    }
+    for (i = 0; i < inorderSize; i++) {
+        node_add(preorder[i], i, preorderSize, pre_heads);
+    }
+
+    int last_index, level = 0;
+    struct TreeNode **stack = malloc(preorderSize * sizeof(*stack));
+    struct TreeNode *tn, *root = NULL;
+    for (i = 0; i < preorderSize; i++) {
+        if (i == 0) {
+            tn = root = node_new(preorder[0]);
+            last_index = find(preorder[0], inorderSize, in_heads);
+            stack[level++] = root;
+        } else {
+            int index = find(preorder[i], inorderSize, in_heads);
+            if (index < last_index) {
+                tn->left = node_new(preorder[i]);
+                tn = tn->left;
+            } else {
+                for (j = index - 1; j >= 0; j--) {
+                    if (find(inorder[j], preorderSize, pre_heads) < i) {
+                        break;
+                    }
+                }
+                /* find the parent of the right child */
+                while (stack[--level]->val != inorder[j]) {}
+                tn = stack[level++];
+                tn->right = node_new(preorder[i]);
+                tn = tn->right;
+            }
+            stack[level++] = tn;
+            last_index = index;
+        }
+    }
+
+    return root;
+#else
+    return recursive(preorder, 0, preorderSize - 1, inorder, 0, inorderSize - 1, in_heads, inorderSize);
+#endif
+}
+
+static void dump(struct TreeNode *node)
+{
+    if (node == NULL) {
+        printf("# ");
+        return;
+    }
+    printf("%d ", node->val);
+    dump(node->left);
+    dump(node->right);
+}
+
+int main(void)
+{
+    //int preorder[] = { 8,4,2,1,3,6,5,7,12,10,9,11,14,13,15 };
+    //int inorder[] = { 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 };
+    int preorder[] = { 7,-10,-4,3,-1,2,-8,11 };
+    int inorder[] = { -4,-10,3,-1,7,11,-8,2 };
+    //int preorder[] = { 3,2,1 };
+    //int preorder[] = { 3,1,2 };
+    //int preorder[] = { 2,1,3 };
+    //int preorder[] = { 1,3,2 };
+    //int preorder[] = { 1,2,3 };
+    //int inorder[] = { 1,2,3 };
+    int pre_size = sizeof(preorder) / sizeof(*preorder);
+    int in_size = sizeof(inorder) / sizeof(*inorder);
+    struct TreeNode *root = buildTree(preorder, pre_size, inorder, in_size);
+    dump(root);
+    printf("\n");
+    return 0;
+}

106_construct_binary_tree_from_inorder_and_postorder_traversal/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test binary_tree_build.c