CodeVs——T 3305 水果姐逛水果街Ⅱ

  1 #include <cstdio>
  2 
  3 using namespace std;
  4 
  5 const int INF(999999999);
  6 const int N(200000+15);
  7 int n,m,u,v,pri[N],ans;
  8 
  9 int head[N],sumedge;
 10 struct Edge
 11 {
 12     int v,next;
 13     Edge(int v=0,int next=0): v(v),next(next){}
 14 }edge[N<<1];
 15 void ins(int u,int v)
 16 {
 17     edge[++sumedge]=Edge(v,head[u]);
 18     head[u]=sumedge;
 19 }
 20 
 21 #define swap(a,b) {int temp=a;a=b;b=temp;}
 22 #define max(a,b) (a>b?a:b)
 23 #define min(a,b) (a<b?a:b)
 24 
 25 struct Node
 26 {
 27     int dad,maxx,minn,up_down,down_up;
 28 }shop[N][25];
 29 int deep[N],maxx,minn,lca;
 30 void DFS(int x,int fa)
 31 {
 32     deep[x]=deep[fa]+1;
 33     shop[x][0].maxx=max(pri[x],pri[fa]);
 34     shop[x][0].minn=min(pri[x],pri[fa]);
 35     shop[x][0].down_up=max(0,pri[fa]-pri[x]);
 36     shop[x][0].up_down=max(0,pri[x]-pri[fa]);
 37     for(int i=1;shop[x][i-1].dad;i++)
 38     {
 39         shop[x][i].dad=shop[shop[x][i-1].dad][i-1].dad;
 40         shop[x][i].maxx=max(shop[x][i-1].maxx,shop[shop[x][i-1].dad][i-1].maxx);
 41         shop[x][i].minn=min(shop[x][i-1].minn,shop[shop[x][i-1].dad][i-1].minn);
 42         shop[x][i].down_up=max(shop[x][i-1].down_up,shop[shop[x][i-1].dad][i-1].down_up);
 43         shop[x][i].down_up=max(shop[x][i].down_up,shop[shop[x][i-1].dad][i-1].maxx-shop[x][i-1].minn);
 44         shop[x][i].up_down=max(shop[x][i-1].up_down,shop[shop[x][i-1].dad][i-1].up_down);
 45         shop[x][i].up_down=max(shop[x][i].up_down,shop[x][i-1].maxx-shop[shop[x][i-1].dad][i-1].minn);
 46     }
 47     for(int i=head[x];i;i=edge[i].next)
 48     {
 49         int v=edge[i].v;
 50         if(shop[x][0].dad!=v) shop[v][0].dad=x,DFS(v,x);
 51     }
 52 }
 53 
 54 int LCA(int x,int y)
 55 {
 56     if(deep[x]>deep[y]) swap(x,y);
 57     for(int i=24;i>=0;i--)
 58         if(deep[shop[y][i].dad]>=deep[x]) y=shop[y][i].dad;
 59     if(x==y) return x;
 60     for(int i=24;i>=0;i--)
 61         if(shop[x][i].dad!=shop[y][i].dad) x=shop[x][i].dad,y=shop[y][i].dad;
 62     return shop[x][0].dad;
 63 }
 64 /*Node Query(int u,int v)
 65 {
 66     Node ret;
 67     ret.minn=1e9,ret.maxx=-23333,ret.up_down=-23333,ret.down_up=-23333;
 68     for(int i=20;i>=0;i--)
 69         if(deep[shop[u][i].dad]>=deep[v])
 70         {
 71             ret.minn=min(shop[u][i].minn,ret.minn);
 72             ret.maxx=max(shop[u][i].maxx,ret.maxx);
 73             ret.up_down=max(ret.up_down,shop[u][i].maxx-ret.minn);
 74             ret.down_up=max(ret.down_up,ret.maxx-shop[u][i].minn);
 75             u=shop[u][i].dad;
 76         }
 77     minx=ret.minn; maxx=ret.maxx;
 78     return ret;
 79 }*/
 80 int Query(int u,int v)
 81 {
 82     ans=0; minn=INF;maxx=-INF;
 83     lca=LCA(u,v);
 84     int dep1=deep[u]-deep[lca];
 85     if(dep1>0)
 86         for(int i=24;i>=0;i--)
 87             if(dep1&(1<<i))
 88             {
 89                 ans=max(ans,max(shop[u][i].down_up,shop[u][i].maxx-minn));
 90                 minn=min(minn,shop[u][i].minn);
 91                 u=shop[u][i].dad;
 92             }
 93     int dep2=deep[v]-deep[lca];
 94     if(dep2>0)
 95     {
 96         for(int i=24;i>=0;i--)
 97             if(dep2&(1<<i))
 98             {
 99                 ans=max(ans,max(shop[v][i].up_down,maxx-shop[v][i].minn));
100                 maxx=max(maxx,shop[v][i].maxx);
101                 v=shop[v][i].dad;
102             }
103     }
104     return max(ans,maxx-minn);
105 }
106 
107 int main()
108 {
109     scanf("%d",&n);
110     for(int i=1;i<=n;i++)
111         scanf("%d",&pri[i]);
112     for(int i=1;i<n;i++)
113     {
114         scanf("%d%d",&u,&v);
115         ins(u,v); ins(v,u);
116     }
117     DFS(1,0);
118     scanf("%d",&m);
119     for(;m--;)
120     {
121         scanf("%d%d",&u,&v);
122         if(u==v) puts("0");
123         else
124         {
125             /*minx=1e9,maxx=-1e9,ans=-2333333,lca=LCA(u,v);
126             int dep1=deep[u]-deep[lca];
127             int dep2=deep[v]-deep[lca];
128             if(dep1>0) ans=max(ans,Query(u,lca).down_up);
129             else ans=max(ans,Query(lca,u).up_down);
130             if(dep2>0) ans=max(ans,Query(v,lca).down_up);
131             else ans=max(ans,Query(lca,v).up_down);
132             ans=max(ans,maxx-minx);*/
133             printf("%d\n",Query(u,v));
134         }
135     }
136     return 0;
137 }