poj 3277 City Horizon

#include <stdio.h>#include <string.h>#include <algorithm>using namespace std;#define LL __int64const int N = 40005;typedef struct{    LL x1,y1;    LL x2,y2;    LL sum;}Node;Node T[N];LL n;bool cmp(Node a,Node b){    if(a.y2!=b.y2) return a.y2<b.y2;    else    {        if(a.x2!=b.x2) return a.x2<b.x2;        elsereturn a.x1>b.x1;    }}void Cover(LL x1,LL y1,LL x2,LL y2,LL k,LL c){    while(k<n&&(x1>=T[k].x2||x2<=T[k].x1||y1>=T[k].y2||y2<=T[k].y1)) k++;    if(k>=n)    {        T[c].sum+=(x2-x1)*(y2-y1);        return;    }    if(x1<T[k].x1)    {        Cover(x1,y1,T[k].x1,y2,k+1,c);        x1=T[k].x1;    }    if(x2>T[k].x2)    {        Cover(T[k].x2,y1,x2,y2,k+1,c);        x2=T[k].x2;    }    if(y1<T[k].y1)    {        Cover(x1,y1,x2,T[k].y1,k+1,c);        y1=T[k].y1;    }    if(y2>T[k].y2)    {        Cover(x1,T[k].y2,x2,y2,k+1,c);        y2=T[k].y2;    }}int main(){    LL i;    LL a,b,c;    while(~scanf("%I64d",&n))    {        for(i=0;i<n;i++)        { scanf("%I64d%I64d%I64d",&a,&b,&c); T[i].x1=a; T[i].y1=0; T[i].x2=b; T[i].y2=c; T[i].sum=0;        }        stable_sort(T,T+n,cmp);        for(i=n-1;i>=0;i--) Cover(T[i].x1,T[i].y1,T[i].x2,T[i].y2,i+1,i);        LL ans=0;        for(i=0;i<n;i++)ans+=T[i].sum;        printf("%I64dn",ans);    }    return 0;}