Sgu 1, 128

Thesis: a one-man essay in 04 years.

The original line segment tree can be used in this way.

Paste code.

#include<cstdio>#include<iostream>#include<algorithm>using namespace std;const int MAX=10005;class BIT{public:int a[MAX<<1];void insert(int pos,int x){while(pos<MAX*2){a[pos]+=x;pos+=pos&(-pos);}}int query(int pos){int ans=0;while(pos){ans+=a[pos];pos-=pos&(-pos);}return ans;}};struct point{int x,y;};BIT bit;point p[MAX];int n,s[MAX],pos[MAX],up[MAX],L[MAX];int find(int x){if(s[x]!=x) s[x]=find(s[x]);return s[x];}void Union(int x,int y){x=find(x);y=find(y);if(x!=y) s[x]=y;}int cmpx(int a,int b){if(p[a].x!=p[b].x) return p[a].x<p[b].x;return p[a].y<p[b].y;}int cmpy(int a,int b){if(p[a].y!=p[b].y) return p[a].y<p[b].y;return p[a].x<p[b].x;}int deal(){int ans=0,i,j,k,t;for(int i=0;i<n;i++)s[i]=i;sort(pos,pos+n,cmpx);for(i=0;i<n;i+=2){j=pos[i];k=pos[i+1];if(p[j].x!=p[k].x) return 0;ans+=p[k].y-p[j].y;up[j]=k;Union(j,k);}sort(pos,pos+n,cmpy);for(i=0;i<n;i+=2){j=pos[i];k=pos[i+1];if(p[j].y!=p[k].y) return 0;ans+=p[k].x-p[j].x;L[j]=1;Union(j,k);}k=find(0);for(i=1;i<=n-1;i++) if(find(i)!=k) return 0;sort(pos,pos+n,cmpx);for(int i=0;i<n;i++){j=pos[i];k=p[up[j]].y;t=p[j].y;if(up[j]&&bit.query(k+MAX)-bit.query(t+MAX+1)) return 0;if(L[j]) bit.insert(t+MAX+1,1);else bit.insert(t+MAX+1,-1);}return ans;}int main(){scanf("%d",&n);int i;for(int i=0;i<n;i++)scanf("%d%d",&p[i].x,&p[i].y),pos[i]=i;printf("%d\n",deal());return 0;}