二叉树给出两种遍历序列（含中序遍历）创建一颗先序遍历二叉树

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#include <iostream>#include <cstdio>#include <queue>#include <stack>#include <cstring>using namespace std;typedef struct NODE{NODE():key('0'), lchild(NULL), rchild(NULL){}char key;NODE *lchild;NODE *rchild;} Node;void pre_mid(Node *&node, int len, char *pre, char *mid){if(len <= 0) return;node = new Node();node->key = *pre;char *pm = strchr(mid, *pre);int l_len = pm - mid;int r_len = len - l_len - 1;pre_mid(node->lchild, l_len, pre+1, mid);pre_mid(node->rchild, r_len, pre+l_len+1, pm+1);}void mid_after(Node *&node, int len, char *mid, char *after){if(len <= 0) return;node = new Node();node->key = *(after+len-1);char *pm = strchr(mid, node->key);int l_len = pm - mid;int r_len = len - l_len - 1;mid_after(node->lchild, l_len, mid, after);mid_after(node->rchild, r_len, pm+1, after+l_len);}void preorder(Node *node){if(node == NULL) return;stack<Node *> st;st.push(node);while(!st.empty()){Node *cur = st.top();st.pop();cout << cur->key;if(cur->rchild)st.push(cur->rchild);if(cur->lchild)st.push(cur->lchild);}cout << endl;}void midorder(Node *node){if(node == NULL) return;stack<Node *> st;Node *cur = node;while(cur || !st.empty()){while(cur){st.push(cur);cur = cur->lchild;}if(!st.empty()){cur = st.top();st.pop();cout << cur->key;cur = cur->rchild;}}cout << endl;}typedef struct POINT{POINT():node(NULL), flag(false){}POINT(Node *_node = NULL, int _flag = false):node(_node), flag(_flag){}Node *node;bool flag;} Point;void afterorder(Node *node){if(node == NULL) return;stack<Point> st;st.push(Point(node, false));while(!st.empty()){Point &cur = st.top();if(cur.flag){cout << cur.node->key;st.pop();continue;}if(cur.node->rchild)st.push(Point(cur.node->rchild, false));if(cur.node->lchild)st.push(Point(cur.node->lchild, false));cur.flag = true;}cout << endl;}int main(){Node *root = NULL;char *pre = "DBACEGF";char *mid = "ABCDEFG";char *after = "ACBFGED";pre_mid(root, strlen(pre), pre, mid);mid_after(root, strlen(pre), mid, after);preorder(root);midorder(root);afterorder(root);return 0;}
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