1.数组实现二叉树的遍历

#include<iostream>
using namespace std;
int len=9;
void prefind(int n[],int i)
{
	if(i>=len)
	return;
	cout<<n[i]<<" ";
	prefind(n,i*2+1);
	prefind(n,i*2+2);
}
void midfind(int n[],int i)
{
	if(i>=len)
	return;	
	midfind(n,i*2+1);
	cout<<n[i]<<" ";
	midfind(n,i*2+2);
}
void endfind(int n[],int i)
{
	if(i>=len)
	return;	
	endfind(n,i*2+1);	
	endfind(n,i*2+2);	
	cout<<n[i]<<" ";
}
int main()
{
	int n[]={78,56,34,43,4,1,15,2,23};
	prefind(n,0);
	cout<<endl;
	midfind(n,0);
	cout<<endl;
	endfind(n,0);
	return 0;
}

堆排序

小根堆

#include<iostream>
using namespace std;
const int N=1e5+5; 
int s[N],sizes;
void down(int k)
{
    int t=k;
    if(k*2<=sizes&&s[k*2]<s[t]) t=k*2;
    if(k*2+1<=sizes&&s[k*2+1]<s[t]) t=k*2+1;
    if(k!=t)
    {
    swap(s[k],s[t]);
    down(t);
    }
}
int main()
{
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=n;i++) cin>>s[i];
    sizes=n;
    for(int i=n/2;i;i--)
    {
        down(i);
    }
    while(m--)
    {
        cout<<s[1]<<" ";
        s[1]=s[sizes];
        sizes--;
        down(1);
    }
    return 0;
}

1.堆的插入
head[++size]=x;
up(size);
2.求最小值（小根堆）
heap[1];
3.删除最小值
head[k]=heap[size];size–;down(1);
4.删除任一元素
heap[k]=heap[size];size–;down(k);up(k);
5.修改任意元素
heap[k]=x;down(k);up(k);

大根堆

#include<iostream>
using namespace std;
const int N=1e5+5; 
int s[N],sizes;
void up(int k)
{
    int t=k;
    if(k*2<=sizes&&s[k*2]>s[t]) t=k*2;
    if(k*2+1<=sizes&&s[k*2+1]>s[t]) t=k*2+1;
    if(k!=t)
    {
    swap(s[k],s[t]);
    up(t);
    }
}
int main()
{
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=n;i++) cin>>s[i];
    sizes=n;
    for(int i=n/2;i;i--)
    {
        up(i);
    }
    while(m--)
    {
        cout<<s[1]<<" ";
        s[1]=s[sizes];
        sizes--;
        up(1);
    }
    return 0;
}