傳送門

Solution:

就是樹鏈剖分入門題啦~

// luogu-judger-enable-o2
#include<bits/stdc++.h>
#define N 30005
#define M 200005
#define lson now<<1
#define rson now<<1|1
#define INF 0x7fffffff
using namespace std;
int n,tot,first[N],val[N];
int father[N],size[N],maxson[N],depth[N],top[N],id[N],sign,wnew[N];
int ans=0;
struct Edge
{int to,next;
}edge[2*N];
inline void addedge(int x,int y)
{tot++;edge[tot].to=y;edge[tot].next=first[x];first[x]=tot;
}
struct node
{int l,r,sum,maxv;
}tree[4*N];
inline void build(int l,int r,int now)
{tree[now].l=l,tree[now].r=r,tree[now].sum=0,tree[now].maxv=0;if(l==r){tree[now].sum=wnew[l];tree[now].maxv=wnew[l];return;}int m=(l+r)>>1;build(l,m,lson);build(m+1,r,rson);tree[now].sum=tree[lson].sum+tree[rson].sum;tree[now].maxv=max(tree[lson].maxv,tree[rson].maxv);
}
inline void update(int now,int x,int k)
{if(tree[now].l==x&&tree[now].r==x){tree[now].sum=k;tree[now].maxv=k;return;}int m=(tree[now].l+tree[now].r)>>1;if(x<=m) update(lson,x,k);else update(rson,x,k);tree[now].sum=tree[lson].sum+tree[rson].sum;tree[now].maxv=max(tree[lson].maxv,tree[rson].maxv);
}
inline void query_sum(int l,int r,int now)
{if(l<=tree[now].l&&tree[now].r<=r) {ans+=tree[now].sum;return;}int m=(tree[now].l+tree[now].r)>>1;if(l<=m)    query_sum(l,r,lson);if(r>m) query_sum(l,r,rson);
}
inline void query_max(int l,int r,int now)
{if(l<=tree[now].l&&tree[now].r<=r) {ans=max(ans,tree[now].maxv);return;}int m=(tree[now].l+tree[now].r)>>1;if(l<=m)    query_max(l,r,lson);if(r>m) query_max(l,r,rson);
}
inline void dfs1(int now,int fa)
{father[now]=fa;size[now]=1;depth[now]=depth[fa]+1;for(int u=first[now];u;u=edge[u].next){int vis=edge[u].to;if(vis==fa) continue;dfs1(vis,now);size[now]+=size[vis];if(size[vis]>size[maxson[now]]) maxson[now]=vis;}
}
inline void dfs2(int now,int topf)
{id[now]=++sign;top[now]=topf;wnew[sign]=val[now];if(maxson[now]) dfs2(maxson[now],topf);for(int u=first[now];u;u=edge[u].next){int vis=edge[u].to;if(vis==father[now]||vis==maxson[now])  continue;dfs2(vis,vis);}
}
inline int qmax(int x,int y)
{int ret=-INF;while(top[x]!=top[y]){if(depth[top[x]]<depth[top[y]]) swap(x,y);//默認x比y深 ans=-INF;query_max(id[top[x]],id[x],1);ret=max(ret,ans);x=father[top[x]];}if(depth[x]<depth[y]) swap(x,y);ans=-INF;query_max(id[y],id[x],1);return max(ret,ans);
}
inline int qsum(int x,int y)
{int ret=0;while(top[x]!=top[y]){if(depth[top[x]]<depth[top[y]]) swap(x,y);//默認x比y淺ans=0;query_sum(id[top[x]],id[x],1);ret+=ans;x=father[top[x]];}if(depth[x]<depth[y]) swap(x,y);ans=0;query_sum(id[y],id[x],1);ret+=ans;return ret;
}
int main()
{cin>>n;for(int i=1;i<=n-1;i++){int x,y;cin>>x>>y;addedge(x,y);addedge(y,x);}for(int i=1;i<=n;i++)   cin>>val[i];dfs1(1,0);dfs2(1,1);build(1,n,1);int Q;cin>>Q;while(Q--){string s;int x,y;cin>>s>>x>>y;if(s=="CHANGE") update(1,id[x],y);if(s=="QMAX") cout<<qmax(x,y)<<'\n';if(s=="QSUM") cout<<qsum(x,y)<<'\n';}return  0;
}

轉載于:https://www.cnblogs.com/Patrickpwq/articles/9467483.html

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