二叉树前序遍历、中序遍历和后序遍历之间还原二叉树

1 // 类定义代码
2 struct TreeNode
3 {
4 char val;
5 TreeNode* left;
6 TreeNode* right;
7 TreeNode(char x) : val(x), left(NULL), right(NULL) {}
8 };
9 int main()
10 {
11 char* pre = "ACDEBF";
12 char* vin = "DCEABF";
13 char* post = "DECFBA";
14 return 0;
15 }

1 TreeNode* BinaryTreeFromOrderings(char* pre, char* vin, int length)
2 {
3 if( length == 0 ) return NULL;
4
5 int rootIndex = 0;
6 // 寻找当前根节点，记录子树元素个数 
7 for(; rootIndex )
8 if( vin[rootIndex] == pre[0] ) break;
9
10 TreeNode* tree = new TreeNode( vin[rootIndex] );
11 // 返回当前左子树
12 tree ->left = BinaryTreeFromOrderings(pre + 1, vin, rootIndex );
13 // 返回当前右子树
14 tree ->right = BinaryTreeFromOrderings(pre + rootIndex + 1, vin + rootIndex + 1, length - (rootIndex + 1));
15
16 return tree;
17 }

TreeNode* BinaryTreeFromPostings(char* vin, char* post, int length)
{
if( length == 0 ) return NULL;
int rootIndex = 0;
// 寻找当前根节点，记录子树元素个数
for(; rootIndex )
if( vin[rootIndex] == post[length - 1]) break;

TreeNode* tree = new TreeNode( vin[rootIndex] );
// 返回当前右子树
tree ->right = BinaryTreeFromPostings(vin + rootIndex + 1, post + rootIndex, length - (rootIndex + 1) );
// 返回当前左子树
tree ->left = BinaryTreeFromPostings(vin, post, rootIndex );

return tree;
}