二叉树的先序遍历（递归和非递归算法）

1.二叉树先序递归算法

#include<stdio.h>
#include<malloc.h>
#define MaxSize 100
typedef char ElemType;
typedef struct node
{
	ElemType data;			
	struct node* lchild;	
	struct node* rchild;	
} BTNode;
void CreateBTree(BTNode*& b, const char* str)
{
	BTNode* st[MaxSize], * p = NULL;
	char ch;
	int j, top, k;
	j = 0;
	top = -1;
	ch = str[j];
	b = NULL;
	while (ch != 0)
	{
		switch (ch)
		{
		case '(':++top; st[top] = p; k = 1; break;
		case ')':--top; break;
		case ',':k = 2; break;
		default:p=(BTNode*)malloc(sizeof(BTNode));
			p->data = str[j]; //p->data=ch;
			p->lchild = NULL;
			p->rchild = NULL;
			if (!b)
				b = p;
			else
			{
				switch (k)
				{
				case 1:st[top]->lchild = p; break;
				case 2:st[top]->rchild = p; break;
				}
			}
		}
		j++;
		ch = str[j];
	}
}
void PreOrder(BTNode* b)
{
	if (b != NULL)
	{
		printf("%c ", b->data);
		PreOrder(b->lchild);
		PreOrder(b->rchild);
	}
}
int main()
{
	BTNode* p;
	CreateBTree(p, "A(B(D(,G)),C(E,F))");
	printf("二叉树的先序递归:\n");
	PreOrder(p);
	return 1;
}

 二叉树先序递归遍历运行结果如下