poj 3277 City Horizon

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//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;
}

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