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Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 262144/262144 K (Java/Others)
Total Submission(s): 439 Accepted Submission(s): 155
/* hdu 5877 线段树 problem: 给你一棵n个节点的有根树,每个节点有价值a[i]. 问有多少个点对(u,v)满足:u是v的祖先且a[u]*a[v] <= k solve: 先找出这个树的根节点. 因为要求u是v的祖先,所以相当于v的父亲到根节点的所有点. 所以可以在树的遍历的时候把走过点的值存入线段树中,当走到第i个节点值 求出线段树中[1,k/a[i]]总共有多少个值就行. 然后递归回退时在把这个点删掉. 数据很大所以再进行一下离散化处理. hhh-2016-09-11 09:22:59 */ #include <algorithm> #include <iostream> #include <cstdlib> #include <stdio.h> #include <cstring> #include <vector> #include <math.h> #include <queue> #include <set> #define lson i<<1 #define rson i<<1|1 #include <map> #define ll long long using namespace std; const int maxn = 200100; int a[maxn]; struct Node { int l,r; int val; } tree[maxn <<2]; void push_up(int i) { tree[i].val= tree[lson].val + tree[rson].val; } void build(int i,int l,int r) { tree[i].l = l,tree[i].r = r; tree[i].val = 0; if(l == r) { return ; } int mid = (tree[i].l + tree[i].r) >> 1; build(lson,l,mid); build(rson,mid+1,r); push_up(i); } void update(int i,int k,int va) { if(tree[i].l == tree[i].r && tree[i].l == k) { tree[i].val += va; return; } int mid = (tree[i].l + tree[i].r) >> 1; if(k <= mid) update(lson,k,va); else update(rson,k,va); push_up(i); } int query(int i,int l,int r) { if(l > r) return 0; if(tree[i].l >= l && tree[i].r <= r) { return tree[i].val; } int tans = 0; int mid = (tree[i].l + tree[i].r ) >> 1; if(l <= mid) tans += query(lson,l,r); if(r > mid) tans += query(rson,l,r); return tans; } struct node { int next; int to; } edge[maxn]; ll k; int ta,tot,n; int head[maxn]; int deep[maxn]; int t[maxn]; void addedge(int from,int to) { edge[tot].to=to; edge[tot].next=head[from]; head[from]=tot++; } ll ans = 0; void dfs(int u,int fa) { int o=lower_bound(t,t+ta,k/a[u])-t; ans+=query(1,0,o); int tk=lower_bound(t,t+ta,a[u])-t; update(1,tk,1); for(int i=head[u]; ~i; i=edge[i].next) { int v=edge[i].to; dfs(v,u); } update(1,tk,-1); } int main() { int T; scanf("%d",&T); while(T--) { scanf("%d %I64d",&n,&k); int cnt=0; for(int i=1; i<=n; i++) { scanf("%I64d",&a[i]); t[cnt++]=a[i]; } for(int i=1; i<=n; i++) t[cnt++]=k/a[i]; sort(t,t+cnt); ta=unique(t,t+cnt)-t; tot=0; memset(head,-1,sizeof(head)); memset(deep,0,sizeof(deep)); for(int i=0; i<n-1; i++) { int u,v; scanf("%d %d",&u,&v); addedge(u,v); deep[v]++; } ans=0; build(1,0,ta); for(int i=1; i<=n; i++) if(deep[i]==0) dfs(i,-1); printf("%I64d\n",ans); } return 0; }
hdu 5877 线段树(2016 ACM/ICPC Asia Regional Dalian Online)
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原文地址:http://www.cnblogs.com/Przz/p/5861042.html