Practice-1

数据结构经常会考：由二叉树前序+中序 判断后序  或 后序+中序判断前序。

下面编程实现作为练习：

#include<iostream>#include<string>#include<queue>using namespace std;struct Node{char data;Node *pleft;Node *pright;Node():pleft(NULL),pright(NULL){}};typedef Node* pNode;class bTree{public:bTree(char* pr, char* mid, char* post):m_pr(pr),m_mid(mid),m_post(post),m_Btree(NULL){};pNode m_Btree;void pr_mid(pNode& tree,int i,int j,int len);//已知前序和中序void post_mid(pNode& tree, int i, int j, int len);//已知后序和中序static void print_post(pNode node){if (!node)return;print_post(node->pleft);print_post(node->pright);cout << node->data;}static void print_pr(pNode node){if (!node)return;cout << node->data;print_pr(node->pleft);print_pr(node->pright);}static void free(pNode node){if (!node)return;free(node->pleft);free(node->pright);delete node;}void print_tree(){queue<pNode> s1,s2;s1.push(m_Btree);while (!s1.empty() || !s2.empty()){if (s1.empty()){while (!s2.empty()){pNode temp = s2.front();s2.pop();cout << temp->data;if (temp->pleft)s1.push(temp->pleft);if (temp->pright)s1.push(temp->pright);}}else{while (!s1.empty()){pNode temp = s1.front();s1.pop();cout << temp->data;if (temp->pleft)s2.push(temp->pleft);if (temp->pright)s2.push(temp->pright);}}cout << endl;}}private:int loc_in_mid(char ch){return string(m_mid, m_mid + strlen(m_mid)).find_first_of(ch);}char *m_pr;//前序char *m_mid;//中序char *m_post;//后序};void bTree::pr_mid(pNode& tree, int i, int j, int len){//i为子树第一个元素在前序的位置，j为子树第一个元素在中序的位置，len为序列长度if (len == 0)return;tree = new Node;tree->data = m_pr[i];int loc = loc_in_mid(tree->data);pr_mid(tree->pleft, i + 1, j, loc - j);pr_mid(tree->pright, i + (loc - j) + 1, loc + 1, len - (loc - j + 1));}void bTree::post_mid(pNode& tree, int i, int j, int len){//i为子树第一个元素在后序的位置，j为子树第一个元素在中序的位置，len为序列长度if (len == 0)return;tree = new Node;tree->data = m_post[i+len-1];int loc = loc_in_mid(tree->data);post_mid(tree->pleft, i, j, loc - j);post_mid(tree->pright, i + (loc - j), loc + 1, len - (loc - j + 1));}int main(){char *pr="ABDHLEKCFG";char *mid = "HLDBEKAFCG";char *post = "LHDKEBFGCA";bTree bt(pr,mid,NULL);//已知前序，中序bt.pr_mid(bt.m_Btree,0,0,strlen(pr));bt.print_tree();cout << "Post: ";bTree::print_post(bt.m_Btree);cout << endl;bTree::free(bt.m_Btree);bt = bTree(NULL, mid, post);//已知后序，中序bt.post_mid(bt.m_Btree,0, 0, strlen(pr));cout << "Pr: ";bTree::print_pr(bt.m_Btree);bTree::free(bt.m_Btree);}