poj 2985 并查集 + 线段树

 

 

此题主要在于构造线段树

struct tnode

{

int left,right,sum;

} ;

sum表示的意思是，具有left到right这个区间的总个数，对于left==right的话，含义更加明显，表示的是具有left个猫的组数。

 

 

此题注意两个地方，1）对于如果处于同一个组的时候不能再做这个change操作，我WA一次,2)不能使用cin，cout，会TLE

 

 

#include<stdlib.h> #include<stdio.h> #include<memory.h> #include<iostream> using namespace std ; const int UFset_M = 200005 ; class UFset { public: int parent[UFset_M] ; UFset() { memset(parent,-1,sizeof(parent)); } ~UFset() {} int find(int x) { if( parent[x]<0 ) return x ; parent[x] = find(parent[x]); return parent[x]; } void unionweight(int x,int y) { int r1=find(x); int r2=find(y); if( r1==r2) return ; if( parent[r1] <= parent[r2] ) // r1's number is more than r2's,so let r2 link to r1 { parent[r1] += parent[r2] ; parent[r2]=r1; } else { parent[r2]+=parent[r1]; parent[r1]=r2; } } }; const int IT_M = 200005 ; int data[IT_M] ; struct tnode { int left,right; int sum ; } ITree[IT_M*40]; void create(int st,int ed,int r=1) { ITree[r].left = st ; ITree[r].right = ed ; if( st==ed) { ITree[r].sum = data[st] ; return ; } int m = (st+ed)>>1; create(st,m,(r<<1)); //create the left subtree create(m+1,ed,(r<<1)+1); //create the right subtree ITree[r].sum = ITree[(r<<1)].sum + ITree[(r<<1)+1].sum ; } // 1 2 ... n void change(int loc , int hm ,int r=1) { //cout<<"#"<<loc<<endl; int m ; while( ITree[r].left != loc || ITree[r].right != loc ) { //cout<<"@"<<r<<endl; ITree[r].sum += hm ; m = (ITree[r].left + ITree[r].right)>>1 ; if( loc <= m ) r=(r<<1) ; else r=(r<<1)+1; } ITree[r].sum += hm ; } void query(int k,int &wh,int r=1) { if( ITree[r].left == ITree[r].right ) { wh = ITree[r].left ; return ; } //cout<<r<<"_"<<ITree[r*2+1].sum<<" "<<ITree[r*2].sum<<endl; if( k > ITree[r*2+1].sum ) // then go to the left { query(k-ITree[r*2+1].sum,wh,r*2) ; } else // go to the right { query(k,wh,r*2+1) ; } } int main() { int n,m; int k; int judge ; int x,y; while(scanf("%d%d",&n,&m)!=EOF) { data[1]=n ; UFset ufs ; create(1,n); while(m--) { scanf("%d",&judge); //cin>>judge ; if( ! judge ) { scanf("%d%d",&x,&y); //cin>>x>>y; //cout<<ufs.parent[ufs.find(x)]<<" "<<ufs.parent[ufs.find(y)]<<endl; if( ufs.find(x) != ufs.find(y) ) { if( ufs.parent[ufs.find(x)] != ufs.parent[ufs.find(y)] ) { change(-ufs.parent[ufs.find(x)],-1) ; change(-ufs.parent[ufs.find(y)],-1) ; } else { change(-ufs.parent[ufs.find(x)],-2) ; } ufs.unionweight(x,y); change(-ufs.parent[ufs.find(x)],1) ; } } else { scanf("%d",&k); //cin>>k ; int ans ; query(k,ans); printf("%d/n",ans); //cout<<ans<<endl; } } } return 0; } /* 7 100 0 1 7 1 1 0 1 7 1 1 */