poj 3277 City Horizon

//数据很大，需要先离散化，然后线段树。

#include<cstdio>

#include<cstring>

#include<iostream>

#include<algorithm>

using namespace std;

const int MAXN=80005;

struct node{

int left, right, mid, cover;

};

struct seg{int x[2], h;}p[40005];

struct HAS{int x, id;}a[80005];

node seg_tree[4*MAXN];

int n, hash[80005];

void make(int l, int r, int num){

seg_tree[num].left=l;

seg_tree[num].right=r;

seg_tree[num].mid=(l+r)/2;

seg_tree[num].cover=0;

if(l+1!=r){

make(l, seg_tree[num].mid, num*2);

make(seg_tree[num].mid, r, num*2+1);

}

}

void insert(int l, int r, int h, int num){

if(seg_tree[num].left==l&&seg_tree[num].right==r){

if(seg_tree[num].cover<h)

seg_tree[num].cover=h;

return;

}

if(r<=seg_tree[num].mid)

insert(l, r, h, 2*num);

else if(l>=seg_tree[num].mid)

insert(l, r, h, 2*num+1);

else {

insert(l, seg_tree[num].mid, h, 2*num);

insert(seg_tree[num].mid, r, h, 2*num+1);

}

}

long long cal(int h, int num){ //由于已经离散化，必须到根节点才能计算

if(h>seg_tree[num].cover)

seg_tree[num].cover=h;

if(seg_tree[num].left+1==seg_tree[num].right)

return (long long)(hash[seg_tree[num].right]-hash[seg_tree[num].left])*seg_tree[num].cover;

return cal(seg_tree[num].cover, num*2)+cal(seg_tree[num].cover, num*2+1);

}

bool cmp(HAS t1, HAS t2){

return t1.x<t2.x;

}

void init(){ //离散化

int i, l, r, h, t;

for(i=0; i<n; i++){

scanf("%d%d%d", &p[i].x[0], &p[i].x[1], &p[i].h);

a[i*2].x=p[i].x[0];

a[i*2+1].x=p[i].x[1];

a[i*2].id=i*2;

a[i*2+1].id=i*2+1;

}

sort(a, a+2*n, cmp);

t=1;

hash[t]=p[a[0].id/2].x[a[0].id%2];

p[a[0].id/2].x[a[0].id%2]=1;

for(i=1; i<2*n; i++){

if(a[i].x>a[i-1].x){

hash[++t]=p[a[i].id/2].x[a[i].id%2];

p[a[i].id/2].x[a[i].id%2]=t;

}

else {

hash[t]=p[a[i].id/2].x[a[i].id%2];

p[a[i].id/2].x[a[i].id%2]=t;

}

}

}

int main(){

//freopen("1.txt", "r", stdin);

scanf("%d", &n);

make(1, 80000, 1);

init();

for(int i=0; i<n; i++)

insert(p[i].x[0], p[i].x[1], p[i].h, 1);

printf("%lld\n", cal(0, 1));

return 0;

}