BZOJ - 2733: [HNOI2012]永无乡
对每个联通块建一棵线段树，并用并查集维护联通块的根。
先开始WA了几次，要注意每次操作都是对联通块的根进行的。
1 #include<cstdio> 2 #include<iostream> 3 using namespace std; 4 inline char nc() { 5 static char b[1<<14],*s=b,*t=b; 6 return s==t&&(t=(s=b)+fread(b,1,1<<14,stdin),s==t)?-1:*s++; 7 } 8 inline void read(int &x) { 9 char b = nc(); x = 0; 10 for (; !isdigit(b); b = nc()); 11 for (; isdigit(b); b = nc()) x = x * 10 + b - '0'; 12 } 13 inline void read(char &x) { 14 for (x = nc(); x != 'B' && x != 'Q'; x = nc()); 15 } 16 const int N = 100010; 17 int rt[N], ls[N*18], rs[N*18], A, r[N], s[N*18]; 18 int n, m, fa[N]; 19 #define lson l, m, ls[rt] 20 #define rson m + 1, r, rs[rt] 21 int find(int x) { 22 return x == fa[x] ? x : fa[x] = find(fa[x]); 23 } 24 inline void upd(int rt) { 25 s[rt] = s[ls[rt]] + s[rs[rt]]; 26 } 27 void add(int p, int l, int r, int &rt) { 28 if (!rt) rt = ++A; 29 if (l == r) return ++s[rt], void(); 30 int m = (l + r) >> 1; 31 if (p <= m) add(p, lson); 32 else add(p, rson); 33 upd(rt); 34 } 35 int merge(int x, int y) { 36 if (!x) return y; 37 if (!y) return x; 38 ls[x] = merge(ls[x], ls[y]); 39 rs[x] = merge(rs[x], rs[y]); 40 s[x] += s[y]; 41 return x; 42 } 43 int query(int k, int l, int r, int rt) { 44 if (l == r) return l; 45 int m = (l + r) >> 1; 46 if (k <= s[ls[rt]]) return query(k, lson); 47 else return query(k - s[ls[rt]], rson); 48 } 49 int query(int x, int k) { 50 if (s[rt[x]] < k) return -1; 51 return r[query(k, 1, n, rt[x])]; 52 } 53 int main() { 54 read(n); read(m); 55 for (int i = 1; i <= n; ++i) fa[i] = i; 56 for (int t, i = 1; i <= n; ++i) 57 read(t), r[t] = i, add(t, 1, n, rt[i]); 58 for (int x, y, i = 0; i < m; ++i) { 59 read(x), read(y); 60 if ((x=find(x)) != (y=find(y))) 61 rt[y] = merge(rt[x], rt[y]), fa[x] = y; 62 } 63 read(m); char op; 64 for (int i = 0, a, b; i < m; ++i) { 65 read(op); read(a); read(b); 66 if (op == 'B') {if ((a=find(a)) != (b=find(b))) rt[b] = merge(rt[a], rt[b]), fa[a] = b;} 67 else printf("%d\n", query(find(a), b)); 68 } 69 return 0; 70 }
