Pre-order sequence, reconstruction of binary tree, output order

The specific algorithm is to use the first letter of the preface (root node) to find the letter, the middle sequence is divided into 2 sections, the previous section is left subtree, length len_l, the following section is right subtree, length len_r. And the length of the pre-order string can be divided into such 2 sections according to the length len_l and len_r of the preceding sequence analysis. Then build it recursively.

Such as:
Pre-sequence "abdhlekcfg";
"HLDBEKAFCG" in the sequence of sequences;
1. Use a to sequence search, divide it into Hldbek and FCG, the length of Zuozi is 6, the right subtree is 3.
2. The pre-sequence sequence is divided into Bdhlek and cfg according to the length of the left and right sub-tree of the preceding sentence.
3. Recursive builds, R (Hldbek,bdhlek) and R (fcg,cfg).

#include <string> #include <iostream> #include <assert.h>using namespace std;struct node{char c; Node *lchild, *rchild;};    Class tree{private:string preorder, inorder;        Node *root;public:tree () {root = NULL;        cout<< "Input string:\n"; while (Cin>>preorder>>inorder)//abdhlekcfg HLDBEKAFCG {rebuildtree (preorder, inorder, Root)            ;            Postorder (root);        cout<< "\ninput-string:\n"; }} ~tree () {} void Rebuildtree (String prestr, String instr, node* &ptemp)//pointer reference {ASSERT (Prestr.le        Ngth () = = Instr.length ());        if (prestr.length () = = 0) {return;        } ptemp = new node;        char c;        c = ptemp->c = Prestr[0];        Ptemp->lchild = NULL;        Ptemp->rchild = NULL;        int pos = Instr.find (c);        int left = pos;        int right = Instr.length ()-pos-1;    if (Left > 0) {        Rebuildtree (PRESTR.SUBSTR (1, left), Instr.substr (0, left), ptemp->lchild); } if (right > 0) {rebuildtree (Prestr.substr (left+1, right), Instr.substr (left+1, right), Ptem        P->rchild);            }} void Postorder (node *p) {if (P! = NULL) {postorder (p->lchild);            Postorder (P->rchild);        cout<<p->c;    }}};void Main () {tree T; System ("Pause");}

　　

Pre-order sequence, reconstruction of binary tree, output order