(遍历二叉树)HDU 1710 Binary Tree Traversals

题意

思路

代码

#include <iostream>
using namespace std;
typedef struct node{
node *l,*r;
int data;
}*treenode;
treenode create(int preorder[], int inorder[], int n,int root){
treenode temp;
for(int i=0;i<n;i++){
if(inorder[i]==preorder[0]){
temp=(treenode)malloc(sizeof(node));
temp->data=inorder[i];
temp->l=create(preorder+1,inorder,i,root);
temp->r=create(preorder+i+1,inorder+i+1,n-i-1,root);
//递归函数中的建树过程其实也可以看作是一个后序遍历
if(temp->data!=root){
cout<<temp->data<<" ";
}
else{
cout<<temp->data<<endl;
}
return temp;
}
}
return NULL;
}
int main(){
int n,preorder[1001],inorder[1001];
while(cin>>n){
for(int i=0;i<n;i++){
cin>>preorder[i];
}
for(int i=0;i<n;i++){
cin>>inorder[i];
}
treenode temp=create(preorder,inorder,n,preorder[0]);
}
return 0;
}

//附上更好理解的代码
#include <iostream>
#include <stack>
using namespace std;

typedef struct Node
{
Node *l,*r;    //struct Node 与 Node  均可以
int num;
}*tree;

tree root;

tree creat(int a[],int b[],int n)
{
tree ss;
for (int i=0;i<n;i++)
{
if (a[0] == b[i])
{
ss = (tree)malloc(sizeof(Node));
ss->num = b[i];
ss->l=creat(a+1,b,i);
ss->r=creat(a+i+1,b+i+1,n-i-1);
return ss;
}
}
return NULL;

}

void post_order(tree h)
{
if (h !=NULL)     //if判断一定不能少，因为到叶子的地方就停止了，
{
post_order(h->l);
post_order(h->r);
if (root == h)
{
cout<<h->num<<endl;
}
else
cout<<h->num<<" ";
}
}

int main()
{
int a[1000],b[1000],n,i;
tree h;
while (cin>>n)
{
for(i=0;i<n;i++)
{
cin>>a[i];
}
for (i=0;i<n;i++)
{
cin>>b[i];
}
root = h = creat(a,b,n);
post_order(h);
}
return 0;
}