#include <iostream>
#include <algorithm>
#include <math.h>
using namespace std;
int n;
struct CPost
{
int L,R;
};
CPost posters[10100];
int x[20200];
int hash[10000010];
struct CNode
{
int L,R;
bool bCovered; //本區間是否已經被完全覆蓋
CNode * pLeft, * pRight;
};
CNode Tree[100000];
int nNodeCount = 0;
int Mid( CNode * pRoot)
{
return (pRoot->L + pRoot->R)/2;
}
void BuildTree( CNode * pRoot, int L, int R)
{
pRoot->L = L;
pRoot->R = R;
pRoot->bCovered = false;
if( L == R )
return;
nNodeCount ++;
pRoot->pLeft = Tree + nNodeCount;
nNodeCount ++;
pRoot->pRight = Tree + nNodeCount;
BuildTree( pRoot->pLeft,L,(L+R)/2);
BuildTree( pRoot->pRight,(L+R)/2 + 1,R);
}
bool Post( CNode *pRoot, int L, int R)
{
if( pRoot->bCovered )
return false;
if( pRoot->L == L && pRoot->R == R) {
pRoot->bCovered = true;
return true;
}
bool bResult ;
if( R <= Mid(pRoot) )
bResult = Post( pRoot->pLeft,L,R);
else if( L >= Mid(pRoot) + 1)
bResult = Post( pRoot->pRight,L,R);
else {
bool b1 = Post(pRoot->pLeft ,L,Mid(pRoot));
bool b2 = Post( pRoot->pRight,Mid(pRoot) + 1,R);
bResult = b1 || b2;
}
//要更新根節點的覆蓋情況
if( pRoot->pLeft->bCovered && pRoot->pRight->bCovered )
pRoot->bCovered = true;
return bResult;
}
int main()
{
int t;
int i,j,k;
scanf("%d",&t);
int nCaseNo = 0;
while(t--) {
nCaseNo ++;
scanf("%d",&n);
int nCount = 0;
for( i = 0;i < n;i ++ ) {
scanf("%d%d", & posters[i].L,& posters[i].R );
x[nCount++] = posters[i].L;
x[nCount++] = posters[i].R;
}
sort(x,x+nCount);
nCount = unique(x,x+nCount) - x; //去掉重復元素
for( i = 0;i < nCount;i ++ )
hash[x[i]] = i;
nNodeCount = 0;
BuildTree( Tree,0,nCount - 1);
int nSum = 0;
for( i = n - 1;i >= 0;i -- ) { // 從后往前看板是否看得見
if( Post(Tree,hash[posters[i].L],hash[posters[i].R]))
nSum ++;
}
printf("%d\n",nSum);
}
return 0;
}
posted on 2010-07-28 22:45
Vontroy 閱讀(298)
評論(0) 編輯 收藏 引用 所屬分類:
線段樹|樹狀數組 、
POJ