UESTC_Rain in ACStar 2015 UESTC Training for Data Structures<Problem L>

L - Rain in ACStar

Time Limit: 9000/3000MS (Java/Others)     Memory Limit: 65535/65535KB (Java/Others)

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Maybe you have heard of Super Cow AC who is the great general of ACM Empire. However, do you know where he is from?

This is one of the ten biggest secrets of this world! And it is time to expose the truth!

Yes, Super Cow AC is from ACStar which is ten million light-year away from our earth. No one, even AC himself, knows how AC came to our home. The only memory in his head is the strange rain in ACStar.

Because of the special gravity of ACStar, the raindrops in ACStar have many funny features. They have arbitrary sizes, color and tastes. The most interesting parts of the raindrops are their shapes. When AC was very young, he found that all the drops he saw in air were convex hull. Once the raindrops fell to the ground, they would be absorb by the soil.

This year is set to be AC-year. In recognition of Great General AC's contribution to our empire, the Emperor decided to build a huge AC park. Inside this park there is a laboratory to simulate the rain in ACStar. As a researcher of this lab, you are appointed to measure the volume of rain absorbed by soil. To simplify this problem, scientists put the rain into two-dimensional plane in which the ground is represented as a straight line and the raindrops are convex polygon. So the area of the graphics stands for the volume of raindrops.

You will receive two types of instructions:

1. R P (This type of instructions tell you sufficient information about the raindrops.)
2. Q A B (Ask you to report the volume of rain absorbed by soil of [A,B].)

Instructions are given in chronological order.

Input

The first line of the inputs is T(no more than 10), which stands for the number of test cases you need to solve.

After T, the inputs will be each test case. The first line of each case will be N(no more than 25000), representing for the numbers of instructions. The following N lines will give instructions of the two types.

For each instruction of type 1, it will be followed by a line listing P (at least 3 and at most 5) points representing the convex polygon of the coming raindrop. The points are started by the leftmost point and are given in counterclockwise order. It's guaranteed that no points of the same raindrop are in the same vertical line.

All numbers are positive integer no more than 1000000000.

Output

For each instruction of type 2, output the corresponding result, which should be printed accurately rounded to three decimals.

It is guaranteed that the result is less than 108.

Sample input and output

Sample Input	Sample Output
1 7 Q 1 100 R 4 10 10 11 10 13 11 12 11 Q 10 11 Q 1 100 R 3 100 20 120 20 110 30 Q 1 100 Q 12 120	0.000 0.250 1.000 1.000 100.250

解题报告

思路很清晰，首先对x离散化,之后的操作就是给某段区间加上一段等差数列.

同时面积的更新当x1 < x2时添加负面积，x1 > x2添加正面积即可

使用线段树来维护，线段树存储四个值:

Double st //左边的增值

Double ed //右边的增值

Double k //单位距离的增值

Double sum //该区间内的S和

！注意下列几点

1.建树从[L，R]→[L,mid] + [mid,R]，不要+个1.。不然中间那段等于是被黑了

2.Updata函数！！！！（本题最需注意的地方），一共三种情况：

1：更新区间[ql,qr]在当前区间[l,r]中mid的左边，此时传递不需要任何改变

2.更新区间[ql,qr]在当前区间[l,r]中mid的右边，此时传递不需要任何改变

3.更新区间[ql,qr]在当前区间[l,r]中mid的两侧，需要将中间的值计算出来然后再次传递下去，同时修改！！！两边的ql,qr值!!!!!!!!!!!!!!!!!!!!!!

注意了以上几点，那么本题也就迎刃而解了

 #include <iostream>
 #include <algorithm>
 #include <cstring>
 #include <cstdio>

 using namespace std;
 const int maxn =  + ;
 int p[maxn*],hash__[maxn*];

 typedef struct Query
 {
   int type,size;
   int x[],y[],id[];
 };

 Query q[maxn];

 typedef struct data
 {
   int l,r,len;
   double st,ed,k,sum;
   void add(double a,double b,double c)
    {
          st += a;
          ed += b;
          k += c;
          sum += (a+b)*len*0.50;
    }
 };

 data tree[maxn*];

 inline double getnext(int x1,int x2,double st,double k)
 {
    return (double)(p[x2] - p[x1]) * k + st; // x2 > x1
 }

 void push_up(int cur)
 {
   tree[cur].sum = tree[cur*].sum + tree[cur*+].sum;
 }

 void push_down(int cur)
 {
   double st = tree[cur].st;
   double ed = tree[cur].ed;
   double k = tree[cur].k;
   int l = tree[cur].l;
   int r = tree[cur].r;
   int mid = l + (r-l)/;
   double midval = getnext(l,mid,st,k);
   tree[cur*].add(st,midval,k);
   tree[cur*+].add(midval,ed,k);
   tree[cur].st = .;
   tree[cur].ed = .;
   tree[cur].k = .;
 }

 void build_tree(int cur,int l,int r)
 {
   tree[cur].l = l , tree[cur].r = r , tree[cur].len = p[r]-p[l];
   tree[cur].st = tree[cur].ed = tree[cur].k = tree[cur].sum = .;
   if (r - l > )
    {
          int mid = l + (r-l) / ;
          build_tree(*cur,l,mid);
          build_tree(*cur+,mid,r);
    }
 }

 void updata(int ql,int qr,int cur,double st,double ed,double k )
 {
    int l = tree[cur].l , r = tree[cur].r;
    if (l >= ql && r <= qr)
     tree[cur].add(st,ed,k);
    else
     {
        push_down(cur);
        int mid = l + (r-l) / ;
        /*
        更新有三种情况
        */
        if (qr <= mid)
         {
             updata(ql,qr,*cur,st,ed,k);  //完全在左边
         }
        else if (ql >= mid)
         {
             updata(ql,qr,*cur+,st,ed,k); //完全在右边
         }
        else
         {
             double news = getnext(ql,mid,st,k); //夹在中间
             updata(ql,qr,*cur,st,news,k);
             updata(mid,qr,*cur+,news,ed,k);
         }
        push_up(cur);
     }
 }

 double query(int ql,int qr,int cur)
 {
    int l = tree[cur].l , r = tree[cur].r;
    if (l >= ql && r <= qr)
     return tree[cur].sum;
    else
     {
        double res = .;
        push_down(cur);
        int mid = l + (r-l) / ;
        if (mid > ql)
         res += query(ql,qr,*cur);
        if (mid < qr)
         res += query(ql,qr,*cur+);
        push_up(cur);
        return res;
     }
 }

 inline double getk(int x1,int y1,int x2,int y2)
 {
    return (double)(y2-y1)/(double)(x2-x1);
 }

 int main(int argc,char *argv[])
 {
   int Case;
   scanf("%d",&Case);
   while(Case--)
    {
          int n;
          int psize = ;
          scanf("%d",&n);
          memset(p,,sizeof(p));
          memset(hash__,,sizeof(hash__));
          memset(q,,sizeof(q));
          for(int i =  ; i < n ; ++ i)
           {
                 char oper[];
                 scanf("%s",oper);
                 if (oper[] == 'R')
                  {
                        q[i].type = ;
                     int size;
                     scanf("%d",&size);
                     q[i].size = size;
                     for(int j =  ; j < size ; ++ j)
                      {
                           int x,y;
                           scanf("%d%d",&x,&y);
                           q[i].x[j] = x , q[i].y[j] = y , q[i].id[j] = psize;
                           p[psize++] = x;
                }
            }
            else
            {
                  q[i].type = ;
                  int x1,x2;
                  scanf("%d%d",&x1,&x2);
                  q[i].x[] = x1;
                  q[i].x[] = x2;
                  q[i].id[] = psize;
                  p[psize++] = x1;
                  q[i].id[] = psize;
                  p[psize++] = x2;
            }
        }
      memcpy(hash__,p,sizeof(int)*psize);
      sort(p,p+psize);
      int c = unique(p,p+psize) - p;
      for(int i =  ; i < psize ; ++ i)
       hash__[i] = lower_bound(p,p+c,hash__[i]) - p;
      build_tree(,,c-); // Tree set
      for(int i =  ; i < n ; ++ i)
       {
             if (q[i].type & )
              {
                   for(int j =  ; j < q[i].size ; ++ j)
                    {
                           int c1 = j;
                           int c2 = (j+)%q[i].size;
                           int t1 = hash__[q[i].id[c1]];
                           int t2 = hash__[q[i].id[c2]];
                           int x1 = q[i].x[c1];
                           int y1 = q[i].y[c1];
                           int x2 = q[i].x[c2];
                           int y2 = q[i].y[c2];
                           if (x1 < x2)
                            {
                               y1 *= -;
                               y2 *= -;
                               double k = getk(x1,y1,x2,y2);  //添加负面积
                        updata(t1,t2,,y1,y2,k);
                     }
                    else
                     {
                        double k = getk(x1,y1,x2,y2);  //添加正面积
                        updata(t2,t1,,y2,y1,k);
                     }
               }
            }
          else
           {
                      int c1 = ;
                          int c2 = ;
                          int t1 = hash__[q[i].id[c1]];
                          int t2 = hash__[q[i].id[c2]];
                          printf("%.3lf\n",query(t1,t2,));
           }
       }
    }
   return ;
 }