2019独角兽企业重金招聘Python工程师标准>>> 
问题描述
从键盘接受输入先序序列，以二叉链表作为存储结构，建立二叉树（以先序来建立）并对其进行中序遍历，然后将遍历结果打印输出。要求采用非递归方法实现。
解题思路
使用栈中间存储树的结点
程序实现
#include
#include
#define FALSE 0
#define TRUE 1
typedef char Datatype;
/*二叉树*/
typedef struct Node {
Datatype data;
struct Node *LChild;
struct Node *RChild;
} BiTNode, *BiTree;
/*链栈*/
typedef struct Stack {
struct Node *node;
struct Stack *next;
} Stack, *SeqStack;
typedef struct {
SeqStack top;
int count;
} LinkStack;
/*栈操作*/
int initStack(LinkStack *stack);
int emptyStack(LinkStack *stack);
int push(LinkStack *stack, BiTree tree);
BiTree pop(LinkStack *stack);
void createBiTree(BiTree *tree);
void traverseTree(BiTree tree, LinkStack *stack);
int main(int argc, char *argv[]) {
BiTree tree;
printf("按先序遍历序列建立二叉树:\n");
createBiTree(&tree);
LinkStack stack;
initStack(&stack);
printf("使用栈后序输出二叉树:\n");
traverseTree(tree, &stack);
return 0;
}
/**
* 初始化一个空栈
*/
int initStack(LinkStack *stack) {
stack->top = (SeqStack)malloc(sizeof(Stack));
if(!stack->top) {
return FALSE;
}
stack->top = NULL;
stack->count = 0;
return TRUE;
}
/**
* 判断栈是否为空
*/
int emptyStack(LinkStack *stack) {
int result = 0;
if (stack->count == 0) {
result = 1;
}
return result;
}
/**
* 入栈操作
*/
int push(LinkStack *stack, BiTree tree) {
SeqStack s = (SeqStack)malloc(sizeof(Stack));
s->node = tree;
s->next = stack->top; /* 把当前的栈顶元素赋值给新结点的直接后继，见图中① */
stack->top = s; /* 将新的结点s赋值给栈顶指针，见图中② */
stack->count++;
return 1;
}
/**
* 出栈操作
*/
BiTree pop(LinkStack *stack) {
BiTree tree;
SeqStack p;
if (emptyStack(stack)) {
return FALSE;
}
tree = stack->top->node;
/*将栈顶结点赋值给p*/
p = stack->top;
/*使得栈顶指针下移一位，指向后一结点*/
stack->top = stack->top->next;
/* 释放结点p */
free(p);
stack->count--;
return tree;
}
void createBiTree(BiTree *tree) {
char ch;
ch = getchar();
if(ch == ' ') {
*tree = NULL;
} else {
//生成一个新结点
*tree = (BiTree)malloc(sizeof(BiTNode));
(*tree)->data = ch;
//生成左子树
createBiTree(&((*tree)->LChild));
//生成右子树
createBiTree(&((*tree)->RChild));
}
}
/**遍历树的结点*/
void traverseTree(BiTree tree, LinkStack *stack) {
if(tree == NULL) {
return;
}
BiTree root = tree;
while (root != NULL || !emptyStack(stack)) {
if (root != NULL) {
push(stack, root);
root = root->LChild;
} else {
root = pop(stack);
printf("%c ", root->data);
root = root->RChild;
}
}
}
运行结果
