PAT-1167（Cartesian Tree）根据中序遍历序列重建最小堆

Cartesian Tree

PAT-1167

• 一开始我使用数组进行存储，但是这样可能会导致无法开足够大的数组，因为树如果是链表状的则无法开这么大的数组（虽然结点很少）。
• 正确的解法还是需要建树，使用指针。

#include<iostream>
#include<cstring>
#include<string>
#include<algorithm>
#include<cstdio>
#include<sstream>
#include<set>
#include<map>
#include<cmath>
#include<vector>
#include<unordered_map>
#include<queue>
using namespace std;
const int INF=0X3F3F3F3F;
int n;
const int maxn=1003;
int a[maxn];//中序遍历
int tree[8*maxn];
int buildHeap(int root,int inl,int inr){
	if(inl>inr)
		return -1;
	int mid=INF;
	int midi=0;
	for(int i=inl;i<=inr;i++){
		if(a[i]<mid){
			mid=a[i];
			midi=i;
		}
	}
	tree[root<<1]=buildHeap(root<<1,inl,midi-1);
	tree[root<<1|1]=buildHeap(root<<1|1,midi+1,inr);
	return mid;
}
int main(){
	cin>>n;
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
	tree[1]=buildHeap(1,0,n-1);
	queue<int>que;
	que.push(1);
	vector<int>ve;
	while(!que.empty()){
		int root=que.front();
		que.pop();
		ve.push_back(tree[root]);
		int lroot=root<<1;
		int rroot=root<<1|1;
		if(tree[lroot]!=-1){
			que.push(lroot);
		}
		if(tree[rroot]!=-1){
			que.push(rroot);
		}
	}
	for(int i=0;i<ve.size();i++){
		if(i==(int)ve.size()-1){
			cout<<ve[i]<<endl;
		}else{
			cout<<ve[i]<<" ";
		}
	}
	return 0;
}

#include<iostream>
#include<cstring>
#include<string>
#include<algorithm>
#include<cstdio>
#include<sstream>
#include<set>
#include<map>
#include<cmath>
#include<vector>
#include<unordered_map>
#include<queue>
using namespace std;
const int INF=0X3F3F3F3F;
int n;
const int maxn=1003;
int a[maxn];//中序遍历
int tree[8*maxn];
struct Node{
	int data;
	Node* left;
	Node* right;
};
Node* buildHeap(int inl,int inr){
	if(inl>inr)
		return NULL;
	int mid=INF;
	int midi=0;
	for(int i=inl;i<=inr;i++){
		if(a[i]<mid){
			mid=a[i];
			midi=i;
		}
	}
	Node* now=new Node();
	now->data=mid;
	now->left=buildHeap(inl,midi-1);
	now->right=buildHeap(midi+1,inr);
	return now;
}
int main(){
	cin>>n;
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
//	cout<<"ue"<<endl;
	Node* root=buildHeap(0,n-1);
	queue<Node*>que;
	que.push(root);
	vector<int>ve;
	while(!que.empty()){
		Node* now=que.front();
		que.pop();
		ve.push_back(now->data);
		if(now->left!=NULL){
			que.push(now->left);
		}
		if(now->right!=NULL){
			que.push(now->right);
		}
	}
	for(int i=0;i<ve.size();i++){
		if(i==(int)ve.size()-1){
			cout<<ve[i]<<endl;
		}else{
			cout<<ve[i]<<" ";
		}
	}
	return 0;
}