BZOJ 2733 [HNOI2012]永无乡 - 启发式合并主席树

Description

1： 查询一个集合内的K大值

2： 合并两个集合

Solution

启发式合并主席树板子

Code

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #define rd read()
 #define rep(i,a,b) for(register int i = (a); i <= (b); ++i)
 #define per(i,a,b) for(register int i = (a); i >= (b); --i)
 using namespace std;

 const int N = 1e5 + 1e4;

 int a[N], id[N], b[N];
 int root[N], lson[N * ], rson[N * ], sum[N * ];
 int n, m, nd_num;
 int father[N], num[N];

 int read() {
     int X = , p = ; char c = getchar();
     for(; c > '' || c < ''; c = getchar()) if(c == '-') p = -;
     for(; c >= '' && c <= ''; c = getchar()) X = X *  + c - '';
     return X * p;
 }

 int cmp(int x, int y) {
     return a[x] < a[y];
 }

 int find_anc(int x) {
     return father[x] == x?  x : father[x] = find_anc(father[x]);
 }

 int fd(int x) {
     return lower_bound(b + , b +  + n, x) - b;
 }

 void ins(int l, int r, int pos, int &nd) {
     if(!nd) nd = ++nd_num;
     sum[nd]++;
     if(l == r) return;
     int mid = (l + r) >> ;
     if(pos <= mid) ins(l, mid, pos, lson[nd]);
     else ins(mid + , r, pos, rson[nd]);
 }

 int query(int l, int r, int k, int nd) {
     if(l == r) return l;
     int mid = (l + r) >> ;
     if(sum[lson[nd]] >= k) return query(l, mid, k, lson[nd]);
     else return query(mid + , r, k - sum[lson[nd]], rson[nd]);
 }

 int mg(int l, int r, int x, int y) {
     if(!x || !y) return x + y;
     int nd = ++nd_num;
     sum[nd] = sum[x] + sum[y];
     if(l == r) return nd;
     int mid = ( l + r) >> ;
     lson[nd] = mg(l, mid, lson[x], lson[y]);
     rson[nd] = mg(mid + , r, rson[x], rson[y]);
     return nd;
 }

 int main()
 {
     n = rd; m = rd;
     rep(i, , n) id[i] = father[i] = i, num[i] = ;
     rep(i, , n) b[i] = a[i] = rd;
     sort(id + , id +  + n, cmp);
     sort(b + , b +  + n);
     rep(i, , n) ins(, n, fd(a[i]), root[i]);
     rep(i, , m) {
         int u = rd, v = rd;
         int x = find_anc(u), y = find_anc(v);
         if(num[x] < num[y]) swap(x, y);
         father[y] = x;
         num[x] += num[y];
         root[x] = mg(, n, root[x], root[y]);
     }
     int T = rd;
     for(; T; T--) {
         char c = getchar();
         while(c != 'Q' && c != 'B') c = getchar();
         int u = rd, v = rd;
         if(c == 'Q') {
             int x = find_anc(u), re;
             if(num[x] < v) {puts("-1"); continue;}
             re = query(, n, v, root[x]);
             printf("%d\n", id[re]);
         }
         else {
             int x = find_anc(u), y = find_anc(v);
             if(x == y) continue;
             if(num[x] < num[y]) swap(x, y);
             father[y] = x;
             num[x] += num[y];
             root[x] = mg(, n, root[x], root[y]);
         }
     }
 }