hdu1264 Counting Squares（线段树+离散化）

 用线段树+离散化做hdu1264比单纯的离散化更为复杂，但是适用范围也更广，今天看这个看得头都晕了，还是有点细节没有处理好，暂时归类到sloving中，明天再继续研究吧，不是AC代码
大意是离散化所有的x线段，然后将所有的y坐标打成一棵线段树，那么每次遍历到一个x[i-1],x[i]区间时，只要将这个区间长度乘以当前所有被覆盖到的y的总长度就可以得到当前的面积，就这样扫描掉所有的x线段，然后把求得的面积累加就可以得到整个图形的面积了

#include <iostream>
using namespace std;
const int size = 110;
struct STree
{
       int l, r;
       int check;
       int cover;      
}stree[2*size];

struct rec
{
       int sx, sy, ex, ey;    
}a[size];
void creat(int num, int l, int r)
{
     stree[num].l = l, stree[num].r = r, stree[num].cover = stree[num].check = 0;
     if (l == r)return ;
     int mid = (l+r) >> 1;
     int p = num << 1;
     creat(p, l, mid);
     creat(p+1, mid+1, r);
}

void insert(int num, int l, int r, int check)
{
     int a = stree[num].l, b = stree[num].r;
     if (a == l && b == r){
        stree[num].check = check;
        if (l != r){
           stree[num].cover = (stree[num].r - stree[num].l)*check;   
        }                 
        else stree[num].cover = check;
     } 
     if (l == r){
        stree[num].cover = 1;
        return ;
     }  
     int mid = (a+b)>> 1;
     int p = num << 1;
     if (r <= mid)insert(p, l, r, check);
     else
          if (l > mid)insert(p+1, l, r, check);
          else insert(p, l, mid, check), insert(p+1, mid+1, r, check);
     stree[num].cover = stree[p].cover + stree[p+1].cover;
}
bool cmp(int x, int y)
{
     return x < y;    
}
int main()
{
    bool is_finish = false;
    int mappx[size];
    while (!is_finish){
          int ii = 0;
          int xx = 0;
          int maxxy = -1;
          while (scanf("%d%d%d%d", &a[ii].sx, &a[ii].sy, &a[ii].ex, &a[ii].ey)){
                if (a[ii].sx == -1)break;
                if (a[ii].sx == -1){is_finish = true;break;}
               
                if (a[ii].sx > a[ii].ex)swap(a[ii].sx, a[ii].ex);
                if (a[ii].sy > a[ii].ey)swap(a[ii].sy, a[ii].ey);
                if (maxxy < a[ii].ey)maxxy = a[ii].ey;
               
                mappx[xx ++]  = a[ii].sx, mappx[xx ++]  = a[ii].ex,
                ii ++;     
          }
         
          sort(mappx, mappx+xx, cmp);
          int sum = 0;
          for (int i = 1; i < xx; i ++){
              creat(1, 1, maxxy);
              if (mappx[i-1] == mappx[i])continue;
              for (int j = 1; j < ii; j ++){
                  if (a[j].sx <= mappx[i-1] && a[j].ex >= mappx[i]){
                     insert(1, a[j].sy, a[j].ey, 1);            
                  }
              }
              sum += (mappx[i]-mappx[i-1])*stree[1].cover;       
          }
          printf("%d\n",sum); 
          if (is_finish)break;   
    }
    return 0;   
}