题目大意:有一些岛屿,一开始由一些无向边连接。后来也有不断的无向边加入,每一个岛屿有个一独一无二的重要度,问任意时刻的与一个岛屿联通的所有岛中重要度第k大的岛的编号是什么。
思路:首先连通性一定要用并查集维护,然后就是联通快内的第k大问题,显然是平衡树。但是并查集的合并怎么搞?可以考虑按秩合并,这样的话就保证每次在平衡树中处理的元素尽量的少,就可以水过这个题了。
注意一下输出-1的判断。
CODE:
#include <map> #include <cstdio> #include <cstring> #include <iostream> #include <algorithm> #define MAX 100010 #define SIZE(a) (a == NULL ? 0:a->size) using namespace std; map<int,int> G; struct Complex{ int val,random,size,cnt; Complex *son[2]; Complex(int _) { val = _; random = rand(); size = cnt = 1; son[0] = son[1] = NULL; } int Compare(int x) { if(x == val) return -1; return x > val; } void Maintain() { size = cnt; if(son[0] != NULL) size += son[0]->size; if(son[1] != NULL) size += son[1]->size; } }; int points,edges,asks; int src[MAX]; int father[MAX],cnt[MAX]; Complex *tree[MAX]; char c[10]; int Find(int x); inline void Rotate(Complex *&a,bool dir); void Insert(Complex *&a,int x); void Delete(Complex *&a,int x); int Kth(Complex *a,int k); int main() { cin >> points >> edges; for(int i = 1;i <= points; ++i) { father[i] = i,cnt[i] = 1; scanf("%d\n",&src[i]); G[src[i]] = i; } for(int x,y,i = 1;i <= edges; ++i) { scanf("%d%d",&x,&y); int fx = Find(x); int fy = Find(y); if(fx != fy) { father[fy] = fx; cnt[fx] += cnt[fy]; } } for(int i = 1;i <= points; ++i) { int fx = Find(i); Insert(tree[fx],src[i]); } cin >> asks; for(int x,y,i = 1;i <= asks; ++i) { scanf("%s%d%d",c,&x,&y); if(c[0] == 'Q') { int fx = Find(x); if(y > cnt[fx]) puts("-1"); else printf("%d\n",G[Kth(tree[fx],y)]); } else { int fx = Find(x); int fy = Find(y); if(fx != fy) { if(cnt[fy] > cnt[fx]) swap(fx,fy); father[fy] = fx; cnt[fx] += cnt[fy]; for(int j = 1;j <= cnt[fy]; ++j) { int temp = Kth(tree[fy],1); Delete(tree[fy],temp); Insert(tree[fx],temp); } } } } return 0; } int Find(int x) { if(father[x] == x) return x; return father[x] = Find(father[x]); } inline void Rotate(Complex *&a,bool dir) { Complex *k = a->son[!dir]; a->son[!dir] = k->son[dir]; k->son[dir] = a; a->Maintain(),k->Maintain(); a = k; } inline void Insert(Complex *&a,int x) { if(a == NULL) { a = new Complex(x); return ; } int dir = a->Compare(x); if(dir == -1) a->cnt++; else { Insert(a->son[dir],x); if(a->son[dir]->random > a->random) Rotate(a,!dir); } a->Maintain(); } void Delete(Complex *&a,int x) { int dir = a->Compare(x); if(dir != -1) Delete(a->son[dir],x); else { if(a->cnt > 1) --a->cnt; else { if(a->son[0] == NULL) a = a->son[1]; else if(a->son[1] == NULL) a = a->son[0]; else { bool _dir = a->son[0]->random > a->son[1]->random; Rotate(a,_dir); Delete(a->son[_dir],x); } } } if(a != NULL) a->Maintain(); } int Kth(Complex *a,int k) { if(k <= SIZE(a->son[0])) return Kth(a->son[0],k); k -= SIZE(a->son[0]); if(k <= a->cnt) return a->val; return Kth(a->son[1],k - a->cnt); }