"Data Structures and Algorithms" experiment two reports // binary tree traversal

Room No. 10-414
Name:
Date: 2018/11/21
Program Name: binary tree traversal and the expression evaluates
Experiment: (b) binary tree traversal

First, the purpose and requirements (needs analysis):

1, the deposit of the binary expression arrays, recursively expression of the binary tree structure, respectively, and then outputs
a preamble, in the sequence and postorder traversals result, and calculate the result of the expression.

Second, the basic ideas, principles and design program description:

(Including the structure of the program, data structures, input / output design, etc. Symbolic Name Description)
1. Program structure: a preorder, preorder, postorder, preorder binary construct, the expression is evaluated configuration function, main constituting the main function.
2. Principle:
1. preorder traversal of a binary tree operation: If the binary tree is empty, the empty; otherwise (1) access to the root node; (2) preorder left subtree; (3) preorder right subtree .
the printf ( "% C", T-> Data);
FirstTransverse (T-> lchild);
FirstTransverse (T-> rchild);
2. binary tree in preorder operation: If the binary tree is empty, the empty; otherwise (1 ) inorder traversal left subtree; (2) access to the root node; (3) in order to traverse the right subtree.
MidTransverse (T-> lchild);
the printf ( "% C", T-> Data);
MidTransverse (T-> rchild);
3. postorder traversal of a binary tree: if the binary tree is empty, the empty; otherwise; ( ) after a preorder left subtree; (2) the right subtree preorder; (3) access to the root node.
FirstTransverse (T-> lchild);
FirstTransverse (T-> rchild);
the printf ( "% C", T-> Data);

Third, the problem of debugging and running programs generated in the process and the measures taken:

1. After traversing the timing, because the wrong position about the sub-tree, causing the output error, debugging for a long time, finally found the error and corrected.
2. When calculating the value of the expression written, encountered a bottleneck, the problem still can not find a program where, also tried other methods, did not run successfully evaluate the expression.

Fourth, the source code and comments:

#include<stdio.h>
#include<stdlib.h>
typedef struct Node{
	char data;
	struct Node *lchild, *rchild;
}Node;//构建结构体 


void FirstTransverse(Node *t){
	if(t==NULL){
		return;
	}
	printf("%c",t->data);
	FirstTransverse(t->lchild);
	FirstTransverse(t->rchild);	
}//先序遍历


void MidTransverse(Node *t){
	if(t==NULL){
		return;
	}
	MidTransverse(t->lchild);
	printf("%c",t->data);
	MidTransverse(t->rchild);
} //中序遍历
void LastTransverse(Node *t){
	if(t==NULL){
		return;
	}
	FirstTransverse(t->lchild);
	FirstTransverse(t->rchild);
	printf("%c",t->data);
} //后序遍历 

Node *PreCreateBitree(Node *t){
	char ch;
	ch=getchar();
	if(ch=='#'){ //空标志 
		t=NULL;
	}
	else{
		t=(Node *)malloc(sizeof(Node));
		t->data=ch;
		t->lchild=PreCreateBitree(t->lchild);
		t->rchild=PreCreateBitree(t->rchild);
	}
	return t;
}//利用先序遍历构建二叉树 


int calculate(Node *t)
{
	printf("%c",t->data);
	FirstTransverse(t->lchild);
	FirstTransverse(t->rchild);
	printf("=");
	if(t==NULL)
	{
		return 0;
	}
	if(t->data <='9'&&t->data >='0')//数据为数字时 
	{
		return (t->data-'0');
	}
	else
	{
		switch(t->data)//运算符号的情况 
		{
			case'+': return calculate(t->lchild) + calculate(t->rchild); // + 
			case'-': return calculate(t->lchild) - calculate(t->rchild); // - 
			case'*': return calculate(t->lchild) * calculate(t->rchild); // * 
			case'/': return calculate(t->lchild) / calculate(t->rchild); // / 
		}
	}
	printf("%c",t->lchild);
	
	
}






int main()
{
	Node *t=NULL;
	t=PreCreateBitree(t);
	printf("\n先序遍历:\n"); 
	FirstTransverse(t); //先序遍历 
	printf("\n\n中序遍历:\n");
	MidTransverse(t);//中序遍历
	printf("\n\n后序遍历:\n");
	LastTransverse(t);// 后序遍历 
	printf("\n\n计算表达式:\n");
	calculate(t); //计算表达式 
	printf("\n");
	return 0; 
}

6.3.5 Operating output:

Sixth, ideas and experience:

Failed to complete the calculation of expression