C语言实现—重建二叉树

根据二叉树的前序序列和中序序列或者后序序列和中序序列均可唯一确定一个二叉树，下面为程序实现：

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>

#define MAX 10
typedef struct Tree{
	int data;
	struct Tree *left;
	struct Tree *right;
}*BiTree, BiNode;

typedef struct list{
	int data[MAX];
	int size;
}Sqlist;
//重建二叉树
BiTree reConstructBinaryTree(Sqlist *pre, Sqlist *in){
	if (in->size == 0){
		return NULL;
	}
	BiTree  b;
	b = NULL;
	if (pre->size!=0){
		b = (BiTree)malloc(sizeof(BiNode));
		b->data = pre->data[0];//前序序列的第一个为根结点
	}
	int i = 0;
	int j = 0;
	int father = 0;
	for (i = 0; i < in->size ; i++){
		if (in->data[i] == pre->data[0]){
			father = i;//找出根结点位于中序序列的位置，可找出根结点的左右子树集合
			break;
		}
	}
	Sqlist pre_left, in_left, pre_right,in_right;//存放根结点的左子树和右子树的前序序列值集合和中序序列值集合
	pre_left.size = 0;
	in_left.size = 0;
	pre_right.size = 0;
	in_right.size = 0;
	for (i = 0; i < father; i++){//左子树值集合
		pre_left.data[i] = pre->data[i + 1];
		pre_left.size++;
		in_left.data[i] = in->data[i];
		in_left.size++;
	}
	for (i = father + 1,j=0; i < in->size; i++,j++){//右子树值集合
		pre_right.data[j] = pre->data[i];
		pre_right.size++;
		in_right.data[j] = in->data[i];
		in_right.size++;
	}

	b->left = reConstructBinaryTree(&pre_left, &in_left);//递归调用将左子树看成完整的一棵树找出根结点作为主根结点的左子树
	b->right = reConstructBinaryTree(&pre_right,&in_right);//递归调用将右子树看成完整的一棵树找出根结点作为主根结点的右子树
	return b;
}
//测试前序输出重建的二叉树
void Pre_Print(BiTree b){
	if (b != NULL){
		printf("%d,", b->data);
	}
	if (b->left != NULL){
		Pre_Print(b->left);
	}
	if (b->right != NULL){
		Pre_Print(b->right);
	}
}
//测试中序输出重建的二叉树
void In_Print(BiTree b){
	if (b->left != NULL){
		In_Print(b->left);
	}
	if (b != NULL){
		printf("%d,", b->data);
	}
	if (b->right != NULL){
		In_Print(b->right);
	}
}
int main(){
	Sqlist  pre;
	pre.size = 0;
	Sqlist  in;
	in.size = 0;
	int i = 0;
	int num = 0;
	printf("请输入共有多少个结点：
");
	scanf("%d", &num);
	printf("请输入先序序列：
");
	for (i = 0; i < num; i++){
		scanf(" %d",&pre.data[i]);
		pre.size++;
	}
	printf("请输入中序序列：
");
	for (i = 0; i < num; i++){
		scanf(" %d", &in.data[i]);
		in.size++;
	}
	reConstructBinaryTree(&pre, &in);
	Pre_Print(reConstructBinaryTree(&pre, &in));
	In_Print(reConstructBinaryTree(&pre, &in));
	system("pause");
	return 0;
}

上述算法使用了归并排序的思想，将每个结点单独看成一颗树，找出结点够归并成一颗完整的树。