BZOJ1803 Spoj1487 Query on a tree III

求子树第k大。。。

对dfs序记时间戳，然后建主席树。。。

不要问我为什么1WA，蒟蒻已经哭晕在厕所T T

（原因是。。。输出了seq[query]...明明是a[query].w 叫你不仔细想2333）

 

 

  1 /**************************************************************
  2     Problem: 1803
  3     User: rausen
  4     Language: C++
  5     Result: Accepted
  6     Time:552 ms
  7     Memory:28936 kb
  8 ****************************************************************/
  9  
 10 #include <cstdio>
 11 #include <algorithm>
 12  
 13 using namespace std;
 14 const int N = 100005;
 15 const int M = 20 * N;
 16  
 17 struct data {
 18     int key, w;
 19     data() {}
 20     data(int _k, int _w) : key(_k), w(_w) {}
 21      
 22     inline bool operator < (const data &x) const {
 23         return key < x.key;
 24     }
 25 } a[N];
 26  
 27 struct edge {
 28     int next, to;
 29     edge() {}
 30     edge(int _n, int _t) : next(_n), to(_t) {}
 31 } e[N << 1];
 32  
 33 struct tree_node {
 34     int fa, v, st, ed;
 35 } tr[N];
 36  
 37 struct seg_node {
 38     int lson, rson, cnt;
 39 } seg[M];
 40  
 41 int n;
 42 int tot, first[N];
 43 int cnt_seq, cnt_seg;
 44 int root[N];
 45  
 46 inline int read() {
 47     int x = 0;
 48     char ch = getchar();
 49     while (ch < '0' || '9' < ch)
 50         ch = getchar();
 51     while ('0' <= ch && ch <= '9') {
 52         x = x * 10 + ch - '0';
 53         ch = getchar();
 54     }
 55     return x;
 56 }
 57  
 58 void Add_Edges(int x, int y) {
 59     e[++tot] = edge(first[x], y), first[x] = tot;
 60     e[++tot] = edge(first[y], x), first[y] = tot;
 61 }
 62  
 63 #define mid (l + r >> 1)
 64 void modify(int &p, int l, int r, int pos) {
 65     seg[++cnt_seg] = seg[p], p = cnt_seg, ++seg[p].cnt;
 66     if (l == r) return;
 67     if (pos <= mid) modify(seg[p].lson, l, mid, pos);
 68     else modify(seg[p].rson, mid + 1, r, pos);
 69 }
 70  
 71 int query(int i, int j, int rank) {
 72     i = root[i], j = root[j];
 73     int l = 1, r = n;
 74     while (l != r) {
 75         if (seg[seg[j].lson].cnt - seg[seg[i].lson].cnt >= rank)
 76             r = mid, i = seg[i].lson, j = seg[j].lson;
 77         else {
 78             rank -= seg[seg[j].lson].cnt - seg[seg[i].lson].cnt;
 79             l = mid + 1, i = seg[i].rson, j = seg[j].rson;
 80         }
 81     }
 82     return l;
 83 }
 84 #undef mid
 85  
 86 void dfs(int p) {
 87     int x, y;
 88     tr[p].st = ++cnt_seq, root[cnt_seq] = root[cnt_seq - 1];
 89     modify(root[cnt_seq], 1, n, tr[p].v);
 90     for (x = first[p]; x; x = e[x].next)
 91         if ((y = e[x].to) != tr[p].fa) {
 92             tr[y].fa = p;
 93             dfs(y);
 94         }
 95     tr[p].ed = cnt_seq;
 96 }
 97  
 98 int main() {
 99     int i, k, Q;
100     n = read();
101     for (i = 1; i <= n; ++i)
102         a[i] = data(read(), i);
103     sort(a + 1, a + n + 1);
104     for (i = 1; i <= n; ++i)
105         tr[a[i].w].v = i;
106     for (i = 1; i < n; ++i)
107         Add_Edges(read(), read());
108     dfs(1);
109  
110     Q = read();
111     while (Q--) {
112         i = read(), k = read();
113         printf("%d\n", a[query(tr[i].st - 1, tr[i].ed, k)].w);
114     }
115     return 0;
116 }
View Code

 

posted on 2014-12-14 12:45  Xs酱~  阅读(205)  评论(0)  编辑  收藏  举报