求区间内个数大于rank的一个数
主席树求一下就好啦！
1 /************************************************************** 2 Problem: 2223 3 User: rausen 4 Language: C++ 5 Result: Accepted 6 Time:704 ms 7 Memory:54712 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <algorithm> 12 13 using namespace std; 14 const int N = 3e5 + 5; 15 const int Cnt_chair = 4500000; 16 17 struct chair_node { 18 chair_node *ls, *rs; 19 int cnt; 20 } *root[N], mempool[Cnt_chair], *cnt_chair = mempool, *null; 21 22 int n, mx, ans; 23 24 inline int read() { 25 int x = 0; 26 char ch = getchar(); 27 while (ch < '0' || '9' < ch) 28 ch = getchar(); 29 while ('0' <= ch && ch <= '9') { 30 x = x * 10 + ch - '0'; 31 ch = getchar(); 32 } 33 return x; 34 } 35 36 #define mid (l + r >> 1) 37 void chair_insert(chair_node *p, chair_node *&q, int l, int r, int x) { 38 (q = ++cnt_chair) -> cnt = p -> cnt + 1; 39 if (l == r) return; 40 if (x <= mid) 41 q -> rs = p -> rs, chair_insert(p -> ls, q -> ls, l, mid, x); 42 else 43 q -> ls = p -> ls, chair_insert(p -> rs, q -> rs, mid + 1, r, x); 44 } 45 46 int chair_query(chair_node *p, chair_node *q, int l, int r, int rank) { 47 if (l == r) return l; 48 if (q -> ls -> cnt - p -> ls -> cnt > rank) 49 return chair_query(p -> ls, q -> ls, l, mid, rank); 50 if (q -> rs -> cnt - p -> rs -> cnt > rank) 51 return chair_query(p -> rs, q -> rs, mid + 1, r, rank); 52 return 0; 53 } 54 #undef mid 55 56 int main() { 57 int Q, i, l, r; 58 n = read(), mx = read(); 59 null = cnt_chair; 60 null -> cnt = 0, null -> ls = null -> rs = null; 61 root[0] = null; 62 for (i = 1; i <= n; ++i) 63 chair_insert(root[i - 1], root[i], 1, mx, read()); 64 Q = read(); 65 while (Q--) { 66 l = read(), r = read(); 67 if (l > r) swap(l, r); 68 ans = chair_query(root[l - 1], root[r], 1, mx, (r - l + 1) >> 1); 69 if (ans == 0) printf("no "); 70 else printf("yes %d ", ans); 71 } 72 return 0; 73 }
(p.s. 数组开小了连WA两发。。。555)