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
" ,MAX(x,y));} if (s[1]== 'S' ) { printf ( "%d
" ,SUM(x,y));} } return 0; } int main(){ init(); work(); return 0; } |