先序构建二叉树及先序遍历二叉树

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/*先序为DLR(D:根节点,L:左子树,R:右子树)
a
/ \
b c
/ \ / \
d * * e
*/
//先序序列为abdce,输入为abd***c*e**(*表示空格,代表空树),输入按满二叉树输入

//每一个节点都是一个子树的根节点

void pre_create_tree(treenode **T){  //递归法char datatemp;fflush(stdin);datatemp=getchar();if(datatemp=='*'){*T=NULL;}else{if((*T=(treenode*)malloc(sizeof(treenode)))==NULL){exit(0);}else{(*T)->data=datatemp;(*T)->lc = (*T)->rc = NULL;pre_create_tree(&(*T)->lc);pre_create_tree(&(*T)->rc);}}}void pre_visit_tree(treenode *T){  //递归法if(T!=NULL){printf("%c ", T->data);pre_visit_tree(T->lc);pre_visit_tree(T->rc);}else{return;}}struct stack_typedef{treenode** stack_head;treenode** stack_top;int stack_used;};typedef struct stack_typedef stack;#define stack_max 1000void stack_init(stack *mystack){if((mystack->stack_head=(treenode**)malloc(sizeof(treenode*)*stack_max))==NULL)exit(0);mystack->stack_used = 0;mystack->stack_top = mystack->stack_head;}void stack_del(stack *mystack){free(mystack->stack_head);}void stack_push(stack *mystack, treenode *data){if(mystack->stack_used<stack_max){*(mystack->stack_top) = data;mystack->stack_used ++;mystack->stack_top ++;}}treenode* stack_pop(stack *mystack){if(mystack->stack_used>0){mystack->stack_used--;mystack->stack_top--;return *mystack->stack_top;}return NULL;}void pre_visit_tree2(treenode *T){  //非递归法，需要使用栈保证输出正确，递归<=>栈stack mystack;stack_init(&mystack);while(1){printf("%c ", T->data);if(T->lc!=NULL){stack_push(&mystack, T);T=T->lc;}else if(T->rc!=NULL){//stack_push(&mystack, T);T=T->rc;}else{//T=stack_pop(&mystack);while(T->rc==NULL&&mystack.stack_used!=0){T=stack_pop(&mystack);}if(T->rc!=NULL)T=T->rc;elsebreak;}};printf("\n");}

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