#C7 b
infectt=function(infected,total=25){
  newinf=infected
  while(infected > 0 & newinf < total){
    infected=infected-1
    count=total-newinf
    while(count > 0){
      count=count-1
      x=runif(1)
      if(x < 0.3) newinf=newinf+1
    }
  }
  return (newinf)
}
uninfectt=function(infected,total=25,uninfect=4){
  x=uninfect
  if(x < infected) return(infected-x)
  return (0)
}
infected_dayss=function(days,total=25,infected=1)
{
  c=0
  while(days > 0){
    days=days-1
    infected=infectt(infected)
    infected=uninfectt(infected)
  }
  return (infected)
}
probb=function(days,k,nrmin=21,total=25,infected=1){
  c=0
  for(i in 1:k){
  x=infected_dayss(days,total,infected)
  if(x >= nrmin) c=c+1
  }
  return (c/k)
}
x=infectt(1)
x
uninfectt(x)
probb(4,1000,nrmin=21)
probb(1,1000,nrmin=1)

```
```{r}
#C7 a,c
infect=function(comp){
  newcomp=comp
  for(i in 1:length(comp)){
    if(comp[i] == 1){
      for(j in 1:length(comp)){
        if(newcomp[j] == 0){
          x=runif(1)
          if(x < 0.3) newcomp[j] = 1
        }
      }
    }
  }
  return (newcomp)
}
uninfect=function(comp){
  infected=vector()
  c=0
  for(i in 1:length(comp)){
    if(comp[i] == 1) {c=c+1; infected[c]=i;}
  }
  if(c > 4) c=4
  while(c > 0){
    index=runif(1,1,length(infected)+1)
    if(infected[index] > 0){
      comp[infected[index]]=0
      infected[index]=0
      c=c-1
    }
  }
  return (comp)
}
all_infected=function(comp)
{
  wasinf=comp
  ok=2
  while(ok == 2){
    comp=infect(comp)
    for(i in 1:length(comp)){
      if(wasinf[i] == 0 & comp[i] == 1) wasinf[i] = 1
    }
    if(sum(wasinf) == length(wasinf)) ok=1
    comp=uninfect(comp)
    if(sum(comp) == 0) ok=0
  }
  return(ok)
}
prob_all_inf=function(nrcomp=25,nr=1000){
  cmp=vector()
  cmp[1]=1
  for(i in 2:nrcomp) cmp[i]=0
  c=0
  for(i in 1:nr){
    c=c+all_infected(cmp)
  }
  return (c/nr)
}
p=prob_all_inf()
p
N=p*(1-p)*(qnorm(0.005)/0.02)^2
N
prob_all_inf(nr=N)