HDU3193 Find the hotel

while(p[i].fs==p[k].fs&&k>=1)  k--;
if(k==0) goal[tmp++]=p[i];

//第一种处理方式 
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<map>
#include<set>
#include<vector>
using namespace std;
using namespace std;
#define pb push_back
#define mp make_pair
#define se second
#define fs first
#define ll long long
#define MS(x,y) memset(x,y,sizeof(x))
#define MC(x,y) memcpy(x,y,sizeof(x))
#define ls o<<1
#define rs o<<1|1
#define SZ(x) ((int)(x).size())
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
typedef pair<int,int> P;
const double eps=1e-9;
const int maxn=10010;
const int N=1e9;
const int mod=1e9+7;

ll read()
{
    ll x=0,f=1;char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
    return x*f;
}
//-----------------------------------------------------------------------------

P p[maxn],goal[maxn];
int n,tmp;
int mi[maxn][20];

void rmq_init(){
    for(int i=1;i<=n;i++) mi[i][0]=p[i].se;
    int k=(int)(log(n*1.0)/log(2.0));
    for(int i=1;i<=k;i++)
    for(int j=1;j<=n;j++)
    {
        mi[j][i]=mi[j][i-1];
        if(j+(1<<(i-1))<=n) mi[j][i]=min(mi[j][i],mi[j+(1<<(i-1))][i-1]);
    }
}

int rmq_min(int l,int r)
{
    int k=(int)(log((r-l+1)*1.0)/log(2.0));
    return min(mi[l][k],mi[r-(1<<k)+1][k]);
}


int main(){
    while(~scanf("%d",&n)){
        for(int i=1;i<=n;i++) scanf("%d%d",&p[i].fs,&p[i].se);
        sort(p+1,p+n+1);
        memset(mi,0,sizeof(mi));
        tmp=0;
        rmq_init();
        goal[tmp++]=p[1];
        for(int i=2;i<=n;i++){
            int k=i;
            while(p[i].fs==p[k].fs&&k>=1)  k--;
            if(k==0) goal[tmp++]=p[i];
            else{
                if(rmq_min(1,k)>=p[i].se) goal[tmp++]=p[i];
            }
        }
        printf("%d\n",tmp);
        for(int i=0;i<tmp;i++) printf("%d %d\n",goal[i].fs,goal[i].se);
    }
    return 0;
}