经典算法之非递归算法实现二叉树前、中、后序遍历

/************************author's email:[e-mail]:2017.12.24非递归算法实现二叉树前、中、后序遍历************************/#include<iostream>using namespace std;#define maxsize 100typedef struct BTNode{char data;struct BTNode *lchild;struct BTNode *rchild;}BTNode,*BTree;BTree createTree();void preorderNonrecursion(BTNode *p);void inorderNonrecursion(BTNode *p);void postorderNonrecursion(BTNode *p);int main(){BTree ptree;ptree = createTree();cout << "非递归算法实现二叉树前序遍历：";preorderNonrecursion(ptree);cout << endl;cout << "非递归算法实现二叉树中序遍历：";inorderNonrecursion(ptree);cout << endl;cout << "非递归算法实现二叉树后序遍历：";postorderNonrecursion(ptree);cout << endl;return 0;}BTree createTree() {BTree pA = (BTNode *)malloc(sizeof(BTNode));BTree pB = (BTNode *)malloc(sizeof(BTNode));BTree pC = (BTNode *)malloc(sizeof(BTNode));BTree pD = (BTNode *)malloc(sizeof(BTNode));BTree pE = (BTNode *)malloc(sizeof(BTNode));BTree pF = (BTNode *)malloc(sizeof(BTNode));BTree pG = (BTNode *)malloc(sizeof(BTNode));BTree pH = (BTNode *)malloc(sizeof(BTNode));BTree pI = (BTNode *)malloc(sizeof(BTNode));pA->data = 'A';pB->data = 'B';pC->data = 'C';pD->data = 'D';pE->data = 'E';pF->data = 'F';pG->data = 'G';pH->data = 'H';pI->data = 'I';pA->lchild = pC;pA->rchild = pB;pC->lchild = pD;pC->rchild = pE;pB->rchild = pF;pB->lchild = NULL;pD->lchild = pG;pD->rchild = NULL;pE->lchild = NULL;pE->rchild = pH;pF->lchild = pI;pF->rchild = NULL;pG->lchild = pG->rchild = NULL;pH->lchild = pH->rchild = NULL;pI->lchild = pI->rchild = NULL;return pA;}//非递归算法实现二叉树前序遍历void preorderNonrecursion(BTNode *p) {if (p != NULL) {BTNode *Stack[maxsize];int top = -1;BTNode *q;Stack[++top] = p;while (top != -1){q = Stack[top--];cout << q ->data;if (q->rchild != NULL)Stack[++top] = q->rchild;if (q->lchild != NULL)Stack[++top] = q->lchild;}}}//非递归算法实现二叉树中序遍历void inorderNonrecursion(BTNode *p) {if (p != NULL) {BTNode *Stack[maxsize];int top = -1;BTNode *q;q = p;while (top != -1 || q != NULL){while (q!= NULL) {      //左孩子存在，则左孩子进栈Stack[++top] = q;q = q->lchild;}if (top != -1) {q = Stack[top--];cout << q->data;q = q->rchild;}}}}/*用两个栈实现非递归二叉树后序遍历，逆后序遍历是将前序遍历过程对左右子树遍历顺序交换，第二个栈用于把逆后序遍历变成后序遍历*/void postorderNonrecursion(BTNode *p){if (p != NULL){BTNode *Stack1[maxsize];int top1 = -1;BTNode *Stack2[maxsize];int top2 = -1;BTNode *q = NULL;Stack1[++top1] = p;while (top1 != -1){q = Stack1[top1--];Stack2[++top2] = q;//栈一出栈元素进入栈二if (q->lchild != NULL)Stack1[++top1] = q->lchild;if (q->rchild != NULL)Stack1[++top1] = q->rchild;}while (top2!= -1){q = Stack2[top2--];cout << q->data;}}}