BZOJ3524 [Poi2014]Couriers

 1 /**************************************************************
 2     Problem: 3524
 3     User: rausen
 4     Language: C++
 5     Result: Accepted
 6     Time:6340 ms
 7     Memory:119984 kb
 8 ****************************************************************/
 9  
10 #include <cstdio>
11 #include <algorithm>
12  
13 using namespace std;
14  
15 struct segment{
16     int lson, rson, cnt;
17 }seg[10000010];
18  
19 int size, m, n, L, R, M, root[510000];
20  
21 void insert(int p, int &q, int l, int r, int X){
22     seg[++size] = seg[p], q = size;
23     ++seg[size].cnt;
24     if (l == r) return;
25     int mid = (l + r) >> 1;
26     if (mid >= X)
27         insert(seg[p].lson, seg[q].lson, l, mid, X);
28     else insert(seg[p].rson, seg[q].rson, mid + 1, r, X);
29 }
30  
31 int query(int Lx, int Rx, int k, int l, int r){
32     if (l == r) return l;
33     int mid = (l + r) >> 1;
34     if (seg[seg[Rx].lson].cnt - seg[seg[Lx].lson].cnt > k)
35         return query(seg[Lx].lson, seg[Rx].lson, k, l, mid);
36     if (seg[seg[Rx].rson].cnt - seg[seg[Lx].rson].cnt > k)
37         return query(seg[Lx].rson, seg[Rx].rson, k, mid + 1, r);
38     return 0;
39 }
40  
41 int main(){
42     scanf("%d%d", &n, &m);
43     size = 0, root[0] = 0;
44     for (int i = 1; i <= n; ++i){
45         scanf("%d", &M);
46         insert(root[i - 1], root[i], 1, n, M);
47     }
48  
49     for (int i = 1; i <= m; ++i){    
50         scanf("%d%d", &L, &R);
51         if (L > R) swap(L, R);
52         M = (R - L + 1) >> 1;
53         printf("%d\n", query(root[L - 1], root[R], M, 1, n));
54     }
55     return 0;
56 }