LUOGU P1505 [国家集训队]旅游 (树链剖分+线段树)
解题思路
快被调死的码农题,,,其实就是一个边权下放到点权的线段树+树剖。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<iostream> #include<cstdio> #include<cstring> #include<algorithm> #include<cstdlib> using namespace std; const int MAXN = 100005; const int inf = 0x3f3f3f3f; inline int rd(){ int x=0,f=1;char ch=getchar(); while(!isdigit(ch)) {f=ch=='-'?0:1;ch=getchar();} while(isdigit(ch)) {x=(x<<1)+(x<<3)+ch-'0';ch=getchar();} return f?x:-x; } int n,m,head[MAXN],cnt=1,to[MAXN<<1],nxt[MAXN<<1],val[MAXN<<1],num; int w[MAXN],wt[MAXN],id[MAXN],top[MAXN],siz[MAXN],son[MAXN],fa[MAXN],dep[MAXN]; int Sum[MAXN<<2],Min[MAXN<<2],Max[MAXN<<2]; bool rev[MAXN<<2],lazy[MAXN<<2]; inline void add(int bg,int ed,int ww){ to[++cnt]=ed,nxt[cnt]=head[bg],head[bg]=cnt,val[cnt]=ww; } void dfs1(int x,int f,int d){ dep[x]=d,fa[x]=f,siz[x]=1;int maxson=-1,u; for(register int i=head[x];i;i=nxt[i]){ u=to[i];if(u==f) continue; dfs1(u,x,d+1);siz[x]+=siz[u];w[u]=val[i]; if(siz[u]>maxson) {maxson=siz[u];son[x]=u;} } } void dfs2(int x,int topf){ top[x]=topf;id[x]=++num;wt[num]=w[x]; if(!son[x]) return;dfs2(son[x],topf);int u; for(register int i=head[x];i;i=nxt[i]){ u=to[i];if(u==fa[x] || u==son[x]) continue; dfs2(u,u); } } inline void pushdown(int x){ rev[x<<1]^=1;rev[x<<1|1]^=1;rev[x]^=1; Sum[x<<1]=-Sum[x<<1];Sum[x<<1|1]=-Sum[x<<1|1]; swap(Min[x<<1],Max[x<<1]);swap(Min[x<<1|1],Max[x<<1|1]); Min[x<<1]=-Min[x<<1];Min[x<<1|1]=-Min[x<<1|1]; Max[x<<1]=-Max[x<<1];Max[x<<1|1]=-Max[x<<1|1]; } void build(int x,int l,int r){ if(l==r) {if(l==1) Min[x]=inf,Max[x]=-inf; else Sum[x]=Min[x]=Max[x]=wt[l];return;} int mid=(l+r)>>1; build(x<<1,l,mid);build(x<<1|1,mid+1,r); Sum[x]=Sum[x<<1]+Sum[x<<1|1]; Min[x]=min(Min[x<<1],Min[x<<1|1]); Max[x]=max(Max[x<<1],Max[x<<1|1]); } void update(int x,int l,int r,int L,int R,int ww){ if(L<=l && r<=R) { if(ww==-inf) {rev[x]^=1;Sum[x]=-Sum[x];swap(Min[x],Max[x]);Min[x]=-Min[x];Max[x]=-Max[x];} else Sum[x]=Min[x]=Max[x]=ww; return; } int mid=(l+r)>>1;if(rev[x]) pushdown(x); if(L<=mid) update(x<<1,l,mid,L,R,ww); if(mid<R) update(x<<1|1,mid+1,r,L,R,ww); Sum[x]=Sum[x<<1]+Sum[x<<1|1]; Min[x]=min(Min[x<<1],Min[x<<1|1]); Max[x]=max(Max[x<<1],Max[x<<1|1]); } int query_Sum(int x,int l,int r,int L,int R){ if(L<=l && r<=R) return Sum[x]; int mid=(l+r)>>1,ret=0;if(rev[x]) pushdown(x); if(L<=mid) ret+=query_Sum(x<<1,l,mid,L,R); if(mid<R) ret+=query_Sum(x<<1|1,mid+1,r,L,R); return ret; } int query_Max(int x,int l,int r,int L,int R){ if(L<=l && r<=R) return Max[x]; int mid=(l+r)>>1,ret=-inf;if(rev[x]) pushdown(x); if(L<=mid) ret=max(ret,query_Max(x<<1,l,mid,L,R)); if(mid<R) ret=max(ret,query_Max(x<<1|1,mid+1,r,L,R)); return ret; } int query_Min(int x,int l,int r,int L,int R){ if(L<=l && r<=R) return Min[x]; int mid=(l+r)>>1,ret=inf;if(rev[x]) pushdown(x); if(L<=mid) ret=min(ret,query_Min(x<<1,l,mid,L,R)); if(mid<R) ret=min(ret,query_Min(x<<1|1,mid+1,r,L,R)); return ret; } void updRev(int x,int y){ while(top[x]!=top[y]){ if(dep[top[x]]<dep[top[y]]) swap(x,y); update(1,1,n,id[top[x]],id[x],-inf); x=fa[top[x]]; } if(dep[x]>dep[y]) swap(x,y); if(x!=y) update(1,1,n,id[x]+1,id[y],-inf); } inline int qSum(int x,int y){ int ret=0; while(top[x]!=top[y]){ if(dep[top[x]]<dep[top[y]]) swap(x,y); ret+=query_Sum(1,1,n,id[top[x]],id[x]); x=fa[top[x]]; } if(dep[x]>dep[y]) swap(x,y); if(x!=y) ret+=query_Sum(1,1,n,id[x]+1,id[y]); return ret; } inline int qMax(int x,int y){ int ret=-inf; while(top[x]!=top[y]){ if(dep[top[x]]<dep[top[y]]) swap(x,y); ret=max(ret,query_Max(1,1,n,id[top[x]],id[x])); x=fa[top[x]]; } if(dep[x]>dep[y]) swap(x,y); if(x!=y) ret=max(ret,query_Max(1,1,n,id[x]+1,id[y])); return ret; } inline int qMin(int x,int y){ int ret=inf; while(top[x]!=top[y]){ if(dep[top[x]]<dep[top[y]]) swap(x,y); ret=min(ret,query_Min(1,1,n,id[top[x]],id[x])); x=fa[top[x]]; } if(dep[x]>dep[y]) swap(x,y);if(x!=y) ret=min(ret,query_Min(1,1,n,id[x]+1,id[y])); return ret; } inline int pre(int x){ return dep[to[x<<1]]>dep[to[x<<1^1]]?to[x<<1]:to[x<<1^1]; } int main(){ // freopen("wrong.out","w",stdout); n=rd();int x,y,z;char s[5]; for(int i=1;i<n;i++){ x=rd()+1,y=rd()+1,z=rd(); add(x,y,z),add(y,x,z); } dfs1(1,0,1);dfs2(1,1);build(1,1,n);m=rd(); while(m--){ scanf("%s",s+1);x=rd(),y=rd(); if(s[1]=='C') update(1,1,n,id[pre(x)],id[pre(x)],y); else if(s[1]=='N') updRev(x+1,y+1); else if(s[1]=='S') printf("%d\n",qSum(x+1,y+1)); else if(s[2]=='A') printf("%d\n",qMax(x+1,y+1)); else printf("%d\n",qMin(x+1,y+1)); } return 0; }