## 1403 - Tough Water Level

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fsps60312
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Posts: 16
Joined: Sun Jan 25, 2015 5:46 pm

### Re: 1403 - Tough Water Level

Hello
I tried to solve the problem by integration and used Simpson's rule to calculate the integration
But keep getting WA
My code (with annotation):

Code: Select all

``````#include<cstdio>
#include<stack>
#include<cmath>
#include<cassert>
using namespace std;
const double EPS=1e-9,PI=acos(-1.0);
char EQUATION[1000000];
int RBRACK[1000000];
bool Digit(const char c){return c>='0'&&c<='9';}
struct Node
{
Node *ch[2];
char o;
double val;
Node(){}
Node(int l,int r):ch{NULL,NULL}
{
while(EQUATION[l]=='('&&RBRACK[l]==r)l++,r--;
assert(EQUATION[l]!='('||RBRACK[l]<r);
//check for illegal charactors
switch(EQUATION[l])
{
case'+':
case'-':
case'*':
case'/':assert(0);
case')':assert(0);
}
switch(EQUATION[r])
{
case'+':
case'-':
case'*':
case'/':assert(0);
case'(':assert(0);
}
int result=0,loc=-1;
for(int i=RBRACK[l]+1;i<=r;i=RBRACK[i+1]+1)
{
switch(EQUATION[i])
{
case'(':
case')':printf("EQUATION[%d]=%c\n",i,EQUATION[i]),assert(0);break;
case'+':
case'-':
if(result<2)result=2,loc=i;
break;
case'*':
case'/':
if(result<1)result=1,loc=i;
break;
}
}
else
{
o=EQUATION[loc];
ch[0]=new Node(l,loc-1);
ch[1]=new Node(loc+1,r);
}
}
void ReadNumber(const int l,const int r)
{
if(EQUATION[l]=='x')assert(l==r),o='x';
else
{
o='d';
val=0.0;
int dotloc;
for(dotloc=l;dotloc<=r&&EQUATION[dotloc]!='.';dotloc++);
for(int i=l;i<dotloc;i++)
{
assert(Digit(EQUATION[i]));
val=val*10.0+(EQUATION[i]-'0');
}
double tmp=0.1;
for(int i=dotloc+1;i<=r;i++,tmp*=0.1)
{
assert(Digit(EQUATION[i]));
val+=tmp*(EQUATION[i]-'0');
}
}
}
double GetValue(const double &x)const
{
switch(o)
{
case'x':return x;
case'd':return val;
case'+':return ch[0]->GetValue(x)+ch[1]->GetValue(x);
case'-':return ch[0]->GetValue(x)-ch[1]->GetValue(x);
case'*':return ch[0]->GetValue(x)*ch[1]->GetValue(x);
case'/':return ch[0]->GetValue(x)/ch[1]->GetValue(x);
default:assert(0);
}
return 0.0;
}
}*NR,*NT;
double H,B;
double Square(const Node *e,const double &x)
{
const double v=e->GetValue(x);
return v*v;
}
double Approximate(const Node *e,const double &l,const double &r)//Simpson's rule
{
const double mid=0.5*(l+r);
return (r-l)*(Square(e,l)+4.0*Square(e,mid)+Square(e,r))/6.0;
}
double ApproximateTorque(const Node *e,const double &o,const double &l,const double &r)//Simpson's rule
{
const double mid=0.5*(l+r);
return (r-l)*(Square(e,l)*(o-l)+4.0*Square(e,mid)*(o-mid)+Square(e,r)*(o-r))/6.0;
}
double Integrate(const Node *e,const double &l,const double &r,const int cnt=0)//cnt: increase accuracy of Simpson's rule
{
double mid=0.5*(l+r);
double s=Approximate(e,l,r),s1=Approximate(e,l,mid),s2=Approximate(e,mid,r);
int nxtc=cnt;
if(fabs(s1+s2-s)<EPS){if(nxtc++>2)return s1+s2;}
else nxtc=0;
return Integrate(e,l,mid,nxtc)+Integrate(e,mid,r,nxtc);
}
double IntegrateTorque(const Node *e,const double &o,const double &l,const double &r,const int cnt=0)//weight point <=> torque==0
{
double mid=0.5*(l+r);
double s=ApproximateTorque(e,o,l,r),s1=ApproximateTorque(e,o,l,mid),s2=ApproximateTorque(e,o,mid,r);
int nxtc=cnt;
if(fabs(s1+s2-s)<EPS){if(nxtc++>2)return s1+s2;}
else nxtc=0;
return IntegrateTorque(e,o,l,mid,nxtc)+IntegrateTorque(e,o,mid,r,nxtc);
}
double CUPC,CUPW;
void GetCUPC()//Get height of Cup's weight point
{
double l=0.0,r=H;
while(r-l>EPS)
{
const double mid=0.5*(l+r);
double v=IntegrateTorque(NR,mid,0.0,H)-IntegrateTorque(NT,mid,B,H);
if(v<0.0)l=mid;
else r=mid;
}
assert(l<=r);
CUPC=0.5*(l+r);
}
void MeasureWater(const double &h,double &w,double &c)//w is weight of water, c is height of weight point
{
w=Integrate(NT,B,h);
double l=B,r=h;
while(r-l>EPS)
{
const double mid=0.5*(l+r);
if(IntegrateTorque(NT,mid,B,h)<0.0)l=mid;
else r=mid;
}
assert(l<=r);
c=0.5*(l+r);
}
double GetWP(const double &h)//Get Weight Point
{
static double w,c;
MeasureWater(h,w,c);
return (CUPW*CUPC+w*c)/(CUPW+w);
}
int main()
{
//	freopen("in.txt","r",stdin);
for(;;)
{
assert(scanf("%lf%lf",&H,&B)==2);
if(H==0.0&&B==0.0)break;
assert(0.0<B&&B<H&&H<=100.0);
for(int type=0;type<=1;type++)
{
scanf("%s",EQUATION);
static int len;
stack<int>stk;
//find corresponding right brack for each left brack
RBRACK[0]=-1;
for(len=0;EQUATION[len];len++,RBRACK[len]=len-1)
{
switch(EQUATION[len])
{
case'(':stk.push(len);break;
case')':RBRACK[stk.top()]=len;stk.pop();break;
}
}
assert(stk.empty());
Node *node=new Node(0,len-1);
if(type==0)NR=node;
else
{
NT=new Node();
NT->o='-';
NT->ch[0]=NR;
NT->ch[1]=node;
}
}
CUPW=Integrate(NR,0.0,H)-Integrate(NT,B,H);
GetCUPC();
CUPW*=2.5;
double l=B,r=H;
//the function of height of weight point must be decreasing, then increasing
//so do this to find the lowest value
while(r-l>EPS)
{
double lm=(2.0*l+r)/3.0,rm=(l+2.0*r)/3.0;
double lmwp=GetWP(lm),rmwp=GetWP(rm);
if(lmwp<rmwp)r=rm;
else l=lm;
}
assert(l<=r);
printf("Pour %.3f litres / %.3f cm of water.\n",0.001*PI*Integrate(NT,B,0.5*(l+r)),0.5*(l+r)-B);
}
return 0;
}``````