BZOJ 1036: [ZJOI2008]树的统计Count(树链剖分)

第一次打树链剖分，也挺容易的嘛~~~，两次dfs后建线段树维护就行了~~~

CDOE:

1

#include<cstdio> #include<iostream> #include<cstring> #include<algorithm> using namespace std; #define maxn 30010 struct edges{     int to,next; }edge[maxn*2]; int next[maxn],l; int addedge(int from,int to){     edge[++l]=(edges){to,next[from]};     next[from]=l;return 0; } int dep[maxn],par[maxn],si[maxn],ch[maxn]; bool b[maxn]; int dfs(int u){     dep[u]=dep[par[u]]+1;     b[u]=0;     si[u]=1;     for (int i=next[u];i;i=edge[i].next)     if (b[edge[i].to]) {          par[edge[i].to]=u;         dfs(edge[i].to);         si[u]+=si[edge[i].to];         if (si[ch[u]]<si[edge[i].to]) ch[u]=edge[i].to;     }     return 0; } int top[maxn],id[maxn],arr[maxn],pos[maxn]; int ind,num; int heavy_edge(int x,bool flag){     if (flag) top[++ind]=x;     id[x]=ind;     b[x]=0;     arr[pos[x]=++num]=x;     if (ch[x]) heavy_edge(ch[x],0);     for (int i=next[x];i;i=edge[i].next)     if (b[edge[i].to]){         heavy_edge(edge[i].to,1);     }     return 0; } struct node{     int l,r,Max,Sum; }t[maxn*4]; int w[maxn]; int buildtree(int x,int l,int r){     t[x].l=l;t[x].r=r;     if (l==r) {t[x].Max=t[x].Sum=w[arr[l]];return 0;}     buildtree(x<<1,l,(l+r)>>1);     buildtree((x<<1)+1,((l+r)>>1)+1,r);     t[x].Max=max(t[x<<1].Max,t[(x<<1)+1].Max);     t[x].Sum=t[x<<1].Sum+t[(x<<1)+1].Sum;     return 0; } int n; int init(){     scanf("%d",&n);     for (int i=1;i<n;i++){     int x,y;     scanf("%d%d",&x,&y);     addedge(x,y);addedge(y,x);     }     memset(b,true,sizeof(b));     dfs(1);     memset(b,true,sizeof(b));     heavy_edge(1,1);     for (int i=1;i<=n;i++) scanf("%d",w+i);     buildtree(1,1,n);     return 0; } int change(int x,int y){     int l=t[x].l,r=t[x].r;     if (y<l||y>r) return 0;     if (l==r) {t[x].Max=t[x].Sum=w[arr[y]];return 0;}     change(x<<1,y);change((x<<1)+1,y);     t[x].Max=max(t[x<<1].Max,t[(x<<1)+1].Max);     t[x].Sum=t[x<<1].Sum+t[(x<<1)+1].Sum;     return 0; } int gmax(int x,int x1,int y1){     int l=t[x].l,r=t[x].r;     if (l>y1||r<x1) return -30002;     if (l>=x1&&r<=y1) return (t[x].Max);     return(max(gmax(x<<1,x1,y1),gmax((x<<1)+1,x1,y1))); } int gsum(int x,int x1,int y1){     int l=t[x].l,r=t[x].r;     if (l>y1||r<x1) return 0;     if (l>=x1&&r<=y1) return (t[x].Sum);     return(gsum(x<<1,x1,y1)+gsum((x<<1)+1,x1,y1)); } int MAX(int l,int r){     int ans=-30001;     while (1){     if (dep[top[id[l]]]<dep[top[id[r]]]) swap(l,r);     if (id[l]!=id[r]) {ans=max(ans,gmax(1,pos[top[id[l]]],pos[l]));l=par[top[id[l]]];}     else {if (dep[l]<dep[r]) swap(l,r);ans=max(ans,gmax(1,pos[r],pos[l]));return ans;}     } } int SUM(int l,int r){     int ans=0;     while (1){     if (dep[top[id[l]]]<dep[top[id[r]]]) swap(l,r);     if (id[l]!=id[r]) {ans+=gsum(1,pos[top[id[l]]],pos[l]);l=par[top[id[l]]];}     else {if (dep[l]<dep[r]) swap(l,r);ans+=gsum(1,pos[r],pos[l]);return ans;}     } } int m; int work(){     scanf("%d",&m);     for (int i=1;i<=m;i++) {     int x,y;char s[10];     scanf("%s%d%d",s,&x,&y);     if (s[0]=='C') {w[x]=y;change(1,pos[x]);}     if (s[1]=='M') {printf("%d\n",MAX(x,y));}     if (s[1]=='S') {printf("%d\n",SUM(x,y));}     }     return 0; } int main(){     init();     work();     return 0; }