函数库 线段树&并查集

<span style="font-family:Microsoft YaHei;font-size:24px;">建造线段树</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">void build(int p,int l,int r)</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">{
    if(l==r) {dat[p]=a[l];return;}
    int mid=(l+r)/2;
    build(p*2,l,mid);
    build(p*2+1,mid+1,r);
    dat[p]=max(dat[p*2],dat[p*2+1]);
}</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">查找线段树
int find(int p,int l,int r,int x,int y)
{
    if((x<=l)&&(r<=y))return dat[p];
    int mid=(l+r)/2;
    if(mid>=y)return find(p*2,l,mid,x,y);
    if(mid<x)return find(p*2+1,mid+1,r,x,y);
    int t=max(find(p*2,l,mid,x,y),find(p*2+1,mid+1,r,x,y));
    return t;
}</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">改变节点数值
void change(int p,int l,int r,int x,int num)
{
    if(l==r) {dat[p]=num;return;}
    int mid=(l+r)/2;
    if(x<=mid) change(p*2,l,mid,x,num);
    else change(p*2+1,mid+1,r,x,num);
    dat[p]=max(dat[p*2],dat[p*2+1]);</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">获取该节点的根</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">int get(int a)
{
    if(par[a]!=a)
    par[a]=get(par[a]);
    return par[a];
}</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">合并两个集合
void merge(int a,int b)
{
    int p1=get(a);
    int p2=get(b);
    if(p1==p2)
        return ;
    par[p2]=p1;
}</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">判断两节点跟师傅相同
bool same(int x,int y)
{
    return get(x)==get(y);
}</span>

<span style="font-family:Microsoft YaHei;font-size:24px;">用并查集时，对每个节点应该初始化它的根。</span>