• 主席树学习笔记 Apare_xzc


    主席树学习笔记

    xzc 2019/4/11


      上次打武大网络赛,除了一道树上第K大的板子题,没搞出来,于是乎,我这周学了主席树,和gdl一起做了专题里的4道题目。

      今天晚上才AC了E题(终于跟上了gdl的进度),这道题做了3天了,感觉有点儿收获,所以想记录下来


    主席树专题vj链接(5道)


    A.K-th Number poj-2104

    分析:
    求静态区间第K大(从小到大第K个),主席树板子题

    我的代码:

      我把前会长Y_Cl给的板子改成了自己的

    • 去掉了num[],直接用a[]存离散化后的值
    • 把指针的写法用数组模拟了,这样更节省空间
    /*
    Status:Accepted
    Time:1672ms
    Memory:22608kB
    Length:1541
    Lang:G++
    Submitted:2019-04-09 20:35:24
    */
    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <algorithm>
    #define For(i,a,b) for(register int i=(a);i<=(b);++i)
    #define Rep(i,a,b) for(register int i=(a);i>=(b);--i)
    #define Mst(a,b) memset(a,(b),sizeof(a)) 
    using namespace std;
    const int maxn = 1e5+10;
    int a[maxn],p[maxn],n,cnt;
    struct Node{
    	int Lchild,Rchild,sum;
    }node[maxn*20];
    int root[maxn*20];
    int update(int left,int right,int v,int p)
    {
    	if(v<left||v>right) return p;
    	int t = cnt++;
    	node[t].Lchild = node[p].Lchild;
    	node[t].Rchild = node[p].Rchild;
    	node[t].sum = node[p].sum + 1;
    	int mid = (left+right)>>1;
    	if(left==right) return t;
    	node[t].Lchild = update(left,mid,v,node[p].Lchild);
    	node[t].Rchild = update(mid+1,right,v,node[p].Rchild);
    	return t;
    }
    void build()
    {
    	cnt = 0;
    	root[0] = cnt++;
    	node[0].Lchild = node[0].Rchild = node[0].sum = 0;
    	For(i,1,n) root[i] = update(1,n,a[i],root[i-1]);
    }
    int query(int left,int right,int k,int rx,int ry)
    {
    	if(left==right) return left;
    	int tot = node[node[ry].Lchild].sum - node[node[rx].Lchild].sum;
    	int mid = (left+right)>>1;
    	if(k<=tot) return query(left,mid,k,node[rx].Lchild,node[ry].Lchild);
    	else return query(mid+1,right,k-tot,node[rx].Rchild,node[ry].Rchild);
    }
    int main()
    {
    	int m;
    	while(scanf("%d%d",&n,&m)!=EOF)
    	{
    		For(i,1,n) scanf("%d",a+i), p[i] = a[i];
    		sort(p+1,p+n+1);
    		For(i,1,n) a[i] = lower_bound(p+1,p+n+1,a[i])-p;
    		build();
    		int l,r,k;
    		while(m--)
    		{
    			scanf("%d%d%d",&l,&r,&k);
    			printf("%d
    ",p[query(1,n,k,root[l-1],root[r])]);
    		}
    	}
    	
    	return 0;
    } 
    
    

    指针写法:

    /*
    Accepted
    1688ms
    22608kB
    1399
    G++
    2019-04-08 20:19:00
    */
    Select Code
    #include <iostream>
    #include <cstdio>
    #include <algorithm>
    #define For(i,a,b) for(register int i=(a);i<=(b);++i)
    using namespace std;
    const int maxn = 1e5+10;
    int a[maxn],p[maxn],n,cnt;
    struct Node{
    	Node * Lchild, * Rchild;
    	int sum;
    }node[maxn*20],*root[maxn*20];
    Node * update(int left,int right,int v,Node * p)
    {
    	if(v<left||v>right) return p;
    	Node * t = &node[cnt++];
    	t->Lchild = p->Lchild;
    	t->Rchild = p->Rchild;
    	t->sum = p->sum + 1; 
    	if(left==right) return t;
    	int mid = (left+right)>>1;
    	t -> Lchild = update(left,mid,v,p->Lchild);
    	t -> Rchild = update(mid+1,right,v,p->Rchild);
    	return t;	
    }
    void build()
    {
    	cnt = 0;
    	root[0] = &node[cnt++];
    	root[0]->Lchild = root[0]->Rchild = root[0];
    	root[0]->sum = 0;
    	For(i,1,n) root[i] = update(1,n,a[i],root[i-1]);
    }
    int query(int left,int right,int k,Node*x,Node*y)
    {
    	if(left==right) return left;
    	int tot = y->Lchild->sum - x->Lchild->sum;
    	int mid = (left+right)>>1;
    	if(k<=tot) return query(left,mid,k,x->Lchild,y->Lchild);
    	else return query(mid+1,right,k-tot,x->Rchild,y->Rchild);
    }
    
    int main()
    {
    	//freopen("in.txt","r",stdin);
    	int m;
    	while(scanf("%d%d",&n,&m)!=EOF)
    	{
    		For(i,1,n) scanf("%d",a+i), p[i] = a[i];
    		sort(p+1,p+1+n);
    		For(i,1,n) a[i] = lower_bound(p+1,p+1+n,a[i])-p;
    		build();
    		int l,r,k;
    		while(m--)
    		{
    			scanf("%d%d%d",&l,&r,&k);
    			printf("%d
    ",p[query(1,n,k,root[l-1],root[r])]);
    		}	
    	} 
    	
    	return 0;	
    }
    

    B.Count on a tree spoj-COT

    题意:
      询问树上第K小

    分析:
      和区间第K大的思想一样,还是要离散化,区间的意义也相同。
      我们知道:一棵树上,两个结点u,v之间的距离可以用这个抽象的公式来求:
    dis(u,v) = dis(u)+dis(v)-2*dis(lca(u,v))
      u,v这条路径上面包含的节点的个数可以这样计算:
    num(u.v) = num(root_to_u) + num(root_to_v) - num(root_to_lca)-num(root_to_fa(lca))
      我们可以先dfs出一棵生成树,然后记录下来书上每个节点x的父节点fa[x]
      建立主席树的时候,每建一棵线段树,不是从数组a前一个点那棵树的基础上建,而是从fa[x]的基础上建树
      我求LCA的方法是dfs+RMQ

    我的代码(指针写的):

    /*
    Status: Accepted
    Time: 1480ms
    Memory: 168960kB
    Length: 3254
    Lang: C++ (gcc 6.3)
    Submitted: 2019-04-08 21:47:25
    */
    #include <iostream>
    #include <cstdio>
    #include <algorithm>
    #include <cstring>
    #define For(i,a,b) for(register int i=(a);i<=(b);++i)
    #define Mst(a,b) memset(a,(b),sizeof(a))
    using namespace std;
    const int maxn = 1e5+100;
    int a[maxn],p[maxn],n,cnt;
    struct Edge{
    	int to,Next;
    }edge[maxn<<1];
    int head[maxn],totEdge;
    int disToRoot[maxn];
    int First[maxn];
    int sequence[maxn<<1];
    int deep[maxn<<1];
    int father[maxn];
    bool vis[maxn];
    struct Node{
    	Node * Lchild, * Rchild;
    	int sum;
    }node[maxn*40],*root[maxn*40];
    Node * update(int left,int right,int v,Node * p);
    void build();
    int query(int left,int right,int k,Node*ru,Node*rv,Node*rlca,Node*rfalca);
    void initG();
    void addedge(int u,int v);
    void dfs(int x,int fa);
    void dfs(int x,int fa,int dep,int &cntOfSeq)
    {
    	father[x] = fa;
    	vis[x] = true;
    	root[x] = update(1,n,a[x],root[fa]);
    	sequence[++cntOfSeq] = x;
    	deep[cntOfSeq] = dep;
    	First[x] = cntOfSeq;
    	for(int i=head[x];i!=-1;i=edge[i].Next)
    	{
    		int to = edge[i].to;
    		if(vis[to]) continue;
    		vis[to] = true;
    		disToRoot[to] = disToRoot[x]+1;
    		dfs(to,x,dep+1,cntOfSeq);
    		sequence[++cntOfSeq] = x;
    		deep[cntOfSeq] = dep;
    	}
    }
    int Min[maxn<<1][20];
    int Log2[maxn<<1]={-1};
    void getST(int n)
    {
    	For(i,1,n) Min[i][0] = i;
    	for(int j=1;(1<<j)<=n;++j)
    	{
    		for(int i=1;i+(1<<j)-1<=n;++i)
    		{
    			int a = Min[i][j-1];
    			int b = Min[i+(1<<(j-1))][j-1];
    			Min[i][j] = deep[a]>deep[b]?b:a;
    		}
    	}
    } 
    int LCA(int x,int y)
    {
    	x = First[x];
    	y = First[y];
    	if(x>y) swap(x,y);
    	int j = Log2[y-x+1];
    	int a = Min[x][j];
    	int b = Min[y-(1<<j)+1][j];
    	return deep[a]>deep[b]?sequence[b]:sequence[a];
    }
    int main()
    {
    	//freopen("in.txt","r",stdin);
    	For(i,1,maxn*2-15) Log2[i] = Log2[i>>1]+1;
    	int m;
    	while(scanf("%d%d",&n,&m)!=EOF)
    	{
    		For(i,1,n) scanf("%d",a+i), p[i] = a[i];
    		sort(p+1,p+1+n);
    		For(i,1,n) a[i] = lower_bound(p+1,p+1+n,a[i])-p;
    		int u,v;
    		initG();
    		For(i,2,n)
    		{
    			scanf("%d%d",&u,&v);
    			addedge(u,v);
    			addedge(v,u);
    		}	
    		build(); //先建一棵空树
    		Mst(vis,0); 
    		int cntOfSequence = 0;
    		dfs(1,0,1,cntOfSequence);
    		int k,lca;
    		getST(2*n-1); 
    		while(m--)
    		{
    			scanf("%d%d%d",&u,&v,&k);
    			lca = LCA(u,v);
    			printf("%d
    ",p[query(1,n,k,root[u],root[v],root[lca],root[father[lca]])]);
    		}	
    	} 
    	
    	
    	return 0;	
    }
    
    void initG()
    {
    	Mst(head,-1);
    	totEdge = 0;
    }
    void addedge(int u,int v)
    {
    	edge[totEdge].to = v;
    	edge[totEdge].Next = head[u];
    	head[u] = totEdge++;
    }
    Node * update(int left,int right,int v,Node * p)
    {
    	if(v<left||v>right) return p;
    	Node * t = &node[cnt++];
    	t->Lchild = p->Lchild;
    	t->Rchild = p->Rchild;
    	t->sum = p->sum + 1; 
    	if(left==right) return t;
    	int mid = (left+right)>>1;
    	t -> Lchild = update(left,mid,v,p->Lchild);
    	t -> Rchild = update(mid+1,right,v,p->Rchild);
    	return t;	
    }
    void build()
    {
    	cnt = 0;
    	root[0] = &node[cnt++];
    	root[0]->Lchild = root[0]->Rchild = root[0];
    	root[0]->sum = 0;
    }
    int query(int left,int right,int k,Node*ru,Node*rv,Node *rlca,Node*rfalca)
    {
    	if(left==right) return left;
    	int tot = ru->Lchild->sum + rv->Lchild->sum 
    	     - rlca->Lchild->sum - rfalca->Lchild->sum;
    	int mid = (left+right)>>1;
    	if(k<=tot) 
    		return query(left,mid,k,ru->Lchild,rv->Lchild,rlca->Lchild,rfalca->Lchild);
    	else 
    		return query(mid+1,right,k-tot,ru->Rchild,rv->Rchild,rlca->Rchild,rfalca->Rchild);
    }
    

    附:2019武大网络赛那道区间第K大(大!)

    • 区间第K大就是区间第cnt-k+1小
    • cnt = deep[u]+deep[v]-deep[lca(u,v)]-deep[fa[lca(u,v)]
    • (deep[u]为节点u在生成树中的深度)

    我的代码:

    /*
    Apr/08/2019 22:10UTC+8	
    CCNU_你们好强啊我们都是面包手	
    F - Climb	
    GNU C++17 Accepted	1294 ms	59200 KB
    */
    Apr/09/2019 06:22UTC+8	CCNU_你们好强啊我们都是面包手	F - Climb	GNU C++17	Accepted	1294 ms	59200 KB
    #include <iostream>
    #include <cstdio>
    #include <algorithm>
    #include <cstring>
    #define For(i,a,b) for(register int i=(a);i<=(b);++i)
    #define Mst(a,b) memset(a,(b),sizeof(a))
    using namespace std;
    const int maxn = 1e5+20;
    int a[maxn],p[maxn],n,cnt;//p离散化 
    struct Edge{
    	int to,Next;
    }edge[maxn<<1];
    int head[maxn],totEdge;//邻接表 
    int First[maxn],sequence[maxn<<1],deep[maxn<<1];
    int father[maxn];
    bool vis[maxn]; //dfs 
    int Min[maxn<<1][20];
    int Log2[maxn<<1]={-1};
    struct Node{
    	Node * Lchild, * Rchild;
    	int sum;
    }node[maxn*20],*root[maxn*20];
    Node * update(int,int,int,Node*); 
    void build(); //建第一课空树(爷爷节点) 
    void initG(); //初始化邻接表 
    void addedge(int u,int v);
    void dfs(int x,int fa,int deep,int&);
    void getST(int n); 
    int LCA(int x,int y);
    int query(int,int,int,Node*,Node*,Node*,Node*);
    int main()
    {
    	//freopen("in.txt","r",stdin);
    	For(i,1,maxn*2-15) Log2[i] = Log2[i>>1]+1;
    	int T,m;scanf("%d",&T);
    	while(T--)
    	{
    		scanf("%d%d",&n,&m);
    		For(i,1,n) scanf("%d",a+i), p[i] = a[i];
    		sort(p+1,p+1+n);
    		For(i,1,n) a[i] = lower_bound(p+1,p+1+n,a[i])-p;
    		int u,v;
    		initG();
    		For(i,2,n)
    		{
    			scanf("%d%d",&u,&v);
    			addedge(u,v);
    			addedge(v,u);
    		}	
    		build(); //先建一棵空树
    		Mst(vis,0); 
    		int cntOfSequence = 0;
    		dfs(1,0,1,cntOfSequence); //dfs生成树的同时,在父节点基础上建立新的线段树 
    		int k,lca;
    		getST(2*n-1); //线性预处理(nlogn) 
    		while(m--)
    		{
    			scanf("%d%d%d",&u,&v,&k); 
    			lca = LCA(u,v);
    			int totNum = deep[First[u]]+deep[First[v]]-deep[First[lca]]-deep[First[father[lca]]];
    			if(k>totNum) //询问的K大于这条路径上所有顶点的个数 
    			{
    				printf("-1
    ");
    				continue;
    			}
    			k = totNum - k+1;
    			printf("%d
    ",p[query(1,n,k,root[u],root[v],root[lca],root[father[lca]])]);
    		}	
    	} 
    	
    	return 0;	
    }
    
    void initG()
    {
    	Mst(head,-1);
    	totEdge = 0;
    }
    void addedge(int u,int v)
    {
    	edge[totEdge].to = v;
    	edge[totEdge].Next = head[u];
    	head[u] = totEdge++;
    }
    void dfs(int x,int fa,int dep,int &cntOfSeq)
    {
    	father[x] = fa;
    	vis[x] = true;
    	root[x] = update(1,n,a[x],root[fa]);
    	sequence[++cntOfSeq] = x;
    	deep[cntOfSeq] = dep;
    	First[x] = cntOfSeq;
    	for(int i=head[x];i!=-1;i=edge[i].Next)
    	{
    		int to = edge[i].to;
    		if(vis[to]) continue;
    		vis[to] = true;
    		dfs(to,x,dep+1,cntOfSeq);
    		sequence[++cntOfSeq] = x;
    		deep[cntOfSeq] = dep;
    	}
    }
    void getST(int n)
    {
    	For(i,1,n) Min[i][0] = i;
    	for(int j=1;(1<<j)<=n;++j)
    	{
    		for(int i=1;i+(1<<j)-1<=n;++i)
    		{
    			int a = Min[i][j-1];
    			int b = Min[i+(1<<(j-1))][j-1];
    			Min[i][j] = deep[a]>deep[b]?b:a;
    		}
    	}
    } 
    int LCA(int x,int y)
    {
    	x = First[x];
    	y = First[y];
    	if(x>y) swap(x,y);
    	int j = Log2[y-x+1];
    	int a = Min[x][j];
    	int b = Min[y-(1<<j)+1][j];
    	return deep[a]>deep[b]?sequence[b]:sequence[a];
    }
    Node * update(int left,int right,int v,Node * p)
    {
    	if(v<left||v>right) return p;
    	Node * t = &node[cnt++];
    	t->Lchild = p->Lchild;
    	t->Rchild = p->Rchild;
    	t->sum = p->sum + 1; 
    	if(left==right) return t;
    	int mid = (left+right)>>1;
    	t -> Lchild = update(left,mid,v,p->Lchild);
    	t -> Rchild = update(mid+1,right,v,p->Rchild);
    	return t;	
    }
    void build()
    {
    	cnt = 0;
    	root[0] = &node[cnt++];
    	root[0]->Lchild = root[0]->Rchild = root[0];
    	root[0]->sum = 0;
    }
    int query(int left,int right,int k,Node*ru,Node*rv,Node *rlca,Node*rfalca)
    {
    	if(left==right) return left;
    	int tot = ru->Lchild->sum + rv->Lchild->sum 
    	     - rlca->Lchild->sum - rfalca->Lchild->sum;
    	int mid = (left+right)>>1;
    	if(k<=tot) 
    		return query(left,mid,k,ru->Lchild,rv->Lchild,rlca->Lchild,rfalca->Lchild);
    	else 
    		return query(mid+1,right,k-tot,ru->Rchild,rv->Rchild,rlca->Rchild,rfalca->Rchild);
    }
    
    

    D.Super Mario HDU-4417
    题意:
      一个数列,求区间内元素值<=H的个数

    两种做法:

    1. 主席树
    2. 离线+线段树

    主席树的代码:

    /*
    Status:Accepted
    Time:187ms
    Memory:23708kB
    Length:1690
    Lang:G++
    Submitted:2019-04-09 21:07:54
    */
    //主席树,数组模拟 
    #include <bits/stdc++.h>
    #define For(i,a,b) for(register int i=(a);i<=(b);++i)
    #define Rep(i,a,b) for(register int i=(a);i>=(b);--i)
    #define Mst(a,b) memset(a,(b),sizeof(a))
    #define LL long long
    #define MP make_pair
    #define pb push_back 
    using namespace std;
    const int maxn = 1e5+10; 
    int a[maxn],p[maxn],n,cnt;
    struct Node{
    	int Lchild,Rchild,sum;
    }node[maxn*20];
    int root[maxn*20];
    int update(int left,int right,int v,int p)
    {
    	if(v<left||v>right) return p;
    	int t = cnt++;
    	node[t].Lchild = node[p].Lchild;
    	node[t].Rchild = node[p].Rchild;
    	node[t].sum = node[p].sum+1;
    	if(left==right) return t;
    	int mid = (left+right)>>1;
    	node[t].Lchild = update(left,mid,v,node[p].Lchild);
    	node[t].Rchild = update(mid+1,right,v,node[p].Rchild);
    	return t;
    } 
    void build()
    {
    	cnt = 0;
    	root[0] = cnt++;
    	node[0].Lchild = node[0].Rchild = node[0].sum = 0;
    	For(i,1,n) root[i] = update(1,n,a[i],root[i-1]);
    }
    int query(int left,int right,int qx,int qy,int rx,int ry)
    {
    	if(left>qy || right<qx) return 0;
    	if(qx<=left&&right<=qy) return node[ry].sum - node[rx].sum;
    	int mid = (left+right)>>1;
    	int ansL = query( left,  mid,qx,qy,node[rx].Lchild,node[ry].Lchild);
    	int ansR = query(mid+1,right,qx,qy,node[rx].Rchild,node[ry].Rchild);
    	return ansL + ansR;
    }
    
    int main()
    {
    	//freopen("in.txt","r",stdin);
    	int m,T;scanf("%d",&T);
    	For(ca,1,T)
    	{
    		scanf("%d%d",&n,&m);
    		For(i,1,n) scanf("%d",a+i), p[i] = a[i];
    		sort(p+1,p+n+1);
    		For(i,1,n) a[i] = lower_bound(p+1,p+n+1,a[i])-p;
    		build();
    		int l,r,H;
    		printf("Case %d:
    ",ca);
    		while(m--)
    		{
    			scanf("%d%d%d",&l,&r,&H);
    			H = upper_bound(p+1,p+n+1,H)-p-1;
    			printf("%d
    ",query(1,n,1,H,root[l],root[r+1]));
    		}
    	}
    
    	return 0;
    }
    

    离线+线段树:

    /*
    Status: Accepted
    Time:171ms
    Memory:6236kB
    Length:1892
    Lang:G++
    Submitted:2019-04-09 21:10:02
    */
    //贴的之前erd老师课堂上写的线段树+离线
    #include <bits/stdc++.h>
    #define For(i,a,b) for(register int i=(a);i<=(b);++i)
    #define Rep(i,a,b) for(register int i=(a);i>=(b);--i)
    #define Mst(a,b) memset(a,(b),sizeof(a))
    #define LL long long
    using namespace std;
    const int maxn = 1e5+100;
    struct A{
    	int x,id;
    }a[maxn];
    struct Node{
    	int left,right,sum; //or id
    	int mid(){return (left+right)>>1;}
    }tree[maxn<<2]; 
    struct Re{
    	int L,R,h,id,ans;
    	void input(int _id)
    	{
    		scanf("%d%d%d",&L,&R,&h);
    		id = _id;
    		++L,++R;
    	}
    }r[maxn];
    void build(int left,int right,int pos=1)
    {
    	tree[pos].left = left;
    	tree[pos].right = right;
    	tree[pos].sum = 0;
    	if(tree[pos].left==tree[pos].right) 
    		return;
    	int mid = (left+right)>>1;
    	build(left,mid,pos<<1);
    	build(mid+1,right,pos<<1|1);	
    }
    void Insert(int x,int pos=1)
    {
    	
    	if(tree[pos].left==tree[pos].right)
    	{
    		++tree[pos].sum;
    		return;
    	}
    		
    	int mid = tree[pos].mid();
    	if(x<=mid) Insert(x,pos<<1);
    	else Insert(x,pos<<1|1);
    	tree[pos].sum = tree[pos<<1].sum+tree[pos<<1|1].sum;
    }
    int quire(int left,int right,int pos=1)
    {
    	if(left>tree[pos].right||right<tree[pos].left)
    		return 0;
    	if(left<=tree[pos].left&&right>=tree[pos].right)
    		return tree[pos].sum;
    	int Ls = quire(left,right,pos<<1);
    	int Rs = quire(left,right,pos<<1|1);
    	return Ls+Rs;
    }
    int main()
    {
    	//freopen("in.txt","r",stdin);
    	//freopen("out.txt","w",stdout);
    	int T;scanf("%d",&T);
    	int m,n;
    	For(ca,1,T)
    	{
    		scanf("%d%d",&n,&m);
    		build(1,n); 
    		For(i,1,n) scanf("%d",&a[i].x),a[i].id = i;
    		For(i,0,m-1)
    		{
    			r[i].input(i);
    		}
    		sort(a+1,a+n+1,[](A xa,A xb){return xa.x<xb.x;});
    		sort(r,r+m,[](Re xx,Re yy){return xx.h<yy.h;});
    		int k = 1;
    		For(i,0,m-1) 
    		{
    			while(k<=n&&a[k].x<=r[i].h) Insert(a[k++].id);
    			r[i].ans = quire(r[i].L,r[i].R); 
    		}
    		sort(r,r+m,[](Re xx,Re yy){return xx.id<yy.id;});
    		printf("Case %d:
    ",ca);
    		For(i,0,m-1)
    			printf("%d
    ",r[i].ans);
    	}
    	
    	return 0;	
    } 
    
    

    E-To the moon HDU - 4348
    题意:

    • 维护区间和
    • 一开始给出数列a[n]的初值,时间戳t为0
    • C L R add 更新操作,把数列[L,R]这部分都加上add,并且时间戳t++
    • Q L R 询问操作,询问当前时间下数列区间[L,R]的和
    • H L R h 询问操作,询问过去某个时间h(h<t)的区间和[L,R]
    • B tt 时间点回到过去的tt(tt<t)

    分析:
      可持久化线段树
      每次更新(C操作)的时候,时间戳t++,新建一棵线段树,并记录线段树根节点的在内存池中的编号为root[t]
      询问H时,在root[H]的那棵线段树中查询
      询问当前区间时,在root[t]的线段树中查询
      B操作时,直接把t该为tt,然后cnt=root[tt+1]这样省空间,相当于是delete了后面的所有树(我觉得这一点我写得非常好~)
      int build(left,right)函数用于建立第一棵t=0时的树,返回值为该节点从内存池中分配的下标
      update(left,right,x,y,add,&t,p)函数用引用的方式实现了返回新分配节点的下标,这个几点表示的区间为[left,right],要更新的范围是[x,y],都+add, t用于返回下标,p是先前时间戳为t-1时候的线段树根节点的下标
      采用永久化标记的思想,lazy不push_down;不论是更新还是查询,当前节点代表的区间[left,right]一定包含了要查询或者更新的范围[x,y]。

    • 在更新中,进入函数的节点都是包含了更新范围的,都是要新建的节点,如果两个范围下好重合,那么直接lazy+=add;return;不必再往下新建子节点了
    • 在查询中,进入函数的节点区间一定也是包含了查询范围的,如果恰好重合,那么return sum[t];不然,就分类讨论要查询区间是在左子树,还是右子树,还是跨了mid。
    • 这个[left,righy]一定包含[x,y]的性质使得我们可以直接求出lazy*(y-x+1)
    程序还是跑得飞快的,空间也不多

    代码:

    /*
    Status: Accepted
    Time: 218ms
    Memory: 10816kB
    Length: 2608
    Lang: G++
    Submitted: 2019-04-11 21:40:54
    */
    #include <bits/stdc++.h>
    #define For(i,a,b) for(register int i=(a);i<=(b);++i)
    #define Rep(i,a,b) for(register int i=(a);i>=(b);--i)
    #define Mst(a,b) memset(a,(b),sizeof(a))
    #define LL long long
    #define MP make_pair
    #define pb push_back
    using namespace std;
    const int maxn = 1e5+4;
    const int N = maxn*20;
    int a[maxn];
    int lson[N],rson[N],root[N],n,cnt;
    LL sum[N],lazy[N];
    int build(int left,int right)
    {
        int t = ++cnt;
        lazy[t] = 0;
        if(left==right)
        {
            sum[t] = a[left];
            return t;
        }
        int mid = (left+right)>>1;
        lson[t] = build(left,mid);
        rson[t] = build(mid+1,right);
        sum[t] = sum[lson[t]]+sum[rson[t]];
        return t;
    }
    void update(int left,int right,int x,int y,int add,int &t,int p)
    {
        t = ++cnt; ///该区间[left,right]一定包含要更新的区间[x,y]
        lazy[t] = lazy[p];
        lson[t] = lson[p];
        rson[t] = rson[p];
        sum[t] = sum[p]+1ll*(y-x+1)*add;
        if(left==x&&right==y)
        {
            lazy[t] += add;
            return;
        }
        int mid = (left+right)>>1;
        if(y<=mid) update(left,mid,x,y,add,lson[t],lson[p]);
        else if(x>mid) update(mid+1,right,x,y,add,rson[t],rson[p]);
        else
            update(left,mid,x,mid,add,lson[t],lson[p]),
            update(mid+1,right,mid+1,y,add,rson[t],rson[p]);
    }
    LL query(int left,int right,int qx,int qy,int t)
    {
        if(left==qx&&right==qy) return sum[t];
        LL add = lazy[t]*(qy-qx+1);
        int mid = (left+right)>>1;
        if(qy<=mid) return query(left,mid,qx,qy,lson[t])+add;
        else if(qx>mid) return query(mid+1,right,qx,qy,rson[t])+add;
        else return
            query(left,mid,qx,mid,lson[t])+
            query(mid+1,right,mid+1,qy,rson[t])+add;
    }
    
    int main()
    {
        int m,t,tt,h,l,r,add,ca=0;
        char op[3];
        while(scanf("%d%d",&n,&m)!=EOF)
        {
            For(i,1,n) scanf("%d",a+i);
            cnt = -1;
            root[0] = build(1,n);
            if(ca++) printf("
    ");
            t = 0; ///current time
            while(m--)
            {
                scanf("%s",op);
                switch (op[0])
                {
                    case 'Q':
                        scanf("%d%d",&l,&r);
                        printf("%lld
    ",query(1,n,l,r,root[t]));
                        break;
                    case 'B':
                        scanf("%d",&t);cnt = root[t+1]-1;
                        break;
                    case 'H':
                        scanf("%d%d%d",&l,&r,&tt);
                        printf("%lld
    ",query(1,n,l,r,root[tt]));
                        break;
                    case 'C':scanf("%d%d%d",&l,&r,&add);
                        ++t;
                        update(1,n,l,r,add,root[t],root[t-1]);
                        break;
                }
            }
        }
        return 0;
    }
    
    

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  • 原文地址:https://www.cnblogs.com/Apare-xzc/p/12243652.html
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