坐标离散化

int compress(int *x1,int *x2,int w){
   vector<int> xs;
   for(int i=0;i<N;i++){
     for(int d=-1;d<=1;d++){
        int tx1=x1[i]+d,tx2=x2[i]+d;
        if(1<=tx1&&tx1<=w) xs.push_back(tx1);
        if(1<=tx2&&tx2<=w) xs.push_back(tx2);
     }
   }
   sort(xs.begin(),xs.end());
   xs.erase(unique(xs.begin(),xs.end()),xs.end());
   for(int i=0;i<N;i++){
     x1[i]=find(xs.begin(),xs.end(),x1[i])-xs.begin();
     x2[i]=find(xs.begin(),xs.end(),x2[i])-xs.begin();
   }
   return xs.size();
}