题意：

思路：

线段树求矩形面积的并。。。同 POJ 1151

//By SiriusRen#include 
     
      #include 
      
       using namespace std;#define N 88888int n,u,tot,xx,yy,h[N];long long ans;struct Node{
    int x,h,cover;}node[4*N];struct Tree{
    int l,r,cover,len;}tree[4*N];bool cmp(Node a,Node b){
    return a.x
       
        >1,lson=pos<<1,rson=pos<<1|1;    build(l,mid,lson),build(mid,r,rson);}void push_up(int l,int r,int pos){    if(tree[pos].cover)tree[pos].len=tree[pos].r-tree[pos].l;    else if(l+1==r)tree[pos].len=0;    else tree[pos].len=tree[pos<<1].len+tree[pos<<1|1].len;}void insert(int l,int r,int pos,Node jy){    if(tree[pos].r<=jy.h){tree[pos].cover+=jy.cover,push_up(l,r,pos);return;}    int mid=(l+r)>>1,lson=pos<<1,rson=pos<<1|1;    if(tree[lson].r>=jy.h)insert(l,mid,lson,jy);    else insert(l,mid,lson,jy),insert(mid,r,rson,jy);    push_up(l,r,pos);}int main(){    scanf("%d",&n);    for(int i=1;i<=n;i++){        scanf("%d%d%d",&xx,&yy,&h[i]);        node[++tot].x=xx,node[tot].h=h[i],node[tot].cover=1;        node[++tot].x=yy,node[tot].h=h[i],node[tot].cover=-1;    }    sort(node+1,node+1+tot,cmp),sort(h+1,h+1+n);    u=unique(h+1,h+1+n)-h-1;    build(0,u,1),insert(0,u,1,node[1]);    for(int i=2;i<=tot;i++){        ans+=(long long)(node[i].x-node[i-1].x)*tree[1].len;        insert(0,u,1,node[i]);    }    printf("%lld\n",ans);}