John Prowle
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johnprowle.bsky.social
John Prowle
@johnprowle.bsky.social
36 followers 22 following 46 posts
Critical Care Nephrologist
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johnprowle.bsky.social
No pruning required! Recursively count neighbours of each vertex in the directed graph until you get to your target vertex (count 1) or the end of the road (count 0) with memoisation. See alt text
library(memoise) map2 <- memoise(function(start,end,G){ x=neighbors(G,start,mode="out") if(length(x)==0){return(0)} if(end%in%names(x)){return(1)} else{ m=0 for(i in 1:length(x)){ m=m+map2(x[i],end,G) } return(m)} } ) map2("svr","fft",G11)*map2("fft","dac",G11)*map2("dac","out",G11)
December 12, 2025 at 12:31 AM
johnprowle.bsky.social
I've completed "Movie Theater" - Day 9 - Advent of Code 2025 #AdventOfCode adventofcode.com/2025/day/9
I'm convinced this is an elaborate Star Wars joke. Impossible objective? Movie Theatre? Turn off the targeting computer & 'use the force' to shoot the end of the 'Death Star Trench Run' @was.tl
December 10, 2025 at 12:19 AM
johnprowle.bsky.social
Please consider joining this exciting and cutting edge course in intensive care nephrology in person at ESICM Lives 2025 with a superb international faculty.

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September 10, 2025 at 10:29 AM
johnprowle.bsky.social
Support a QMUL international Critical Care Master's student in our survey on international practices in acute renal replacement therapy!

forms.office.com/e/PEWXmRN9h0
QR code for the survey
May 31, 2025 at 1:52 PM
johnprowle.bsky.social
Just fits in! - igraph components() to define regions. 'Corner' definition in part 2 was the hardest bit...
library(igraph) d24.12<-aoc_get_response(12, session_cookie ) %>% content(encoding = 'UTF-8') %>%read_lines() %>% str_split("",simplify=T) x <- which(nchar(d24.12)==1,arr.ind = T) #just all the coordinates y <- seq(d24.12) #and all the indices mp12 <- NULL for(i in seq(y)){ v <- y[rowSums(cbind(abs(x[,1]-x[i,1]),abs(x[,2]-x[i,2])))==1 & (d24.12[i]==d24.12)] if(length(v>0)){mp12 <- rbind(mp12,matrix(c(rep(i,length(v)),v),ncol=2))} } mp12.1 <- as.vector(t(mp12)) G12 <- make_graph(mp12.1,directed=F) d12 <- components(G12) tot1=NULL for(j in 1:d12$no){ tot <- 0 for(i in seq(d12$csize[j])){ tot <- tot+sum(mp12[,1]==y[d12$membership==j][i])} tot1 <- c(tot1,(4*d12$csize[j]-tot)*d12$csize[j]) } sum(tot1) tot1 <- 0 u <- matrix(c(0,1,1,0,1,1),ncol=2,byrow=T) u1 <- matrix(c(0,-1,1,0,1,-1),ncol=2,byrow=T) u2 <- matrix(c(0,-1,-1,0,-1,-1),ncol=2,byrow=T) u3 <- matrix(c(0,1,-1,0,-1,1),ncol=2,byrow=T) for(j in 1:d12$no){ X <- x[d12$membership==j,] %>% matrix(ncol=2) XX <- apply(X,1,paste,collapse=",") tot <- 0 for(i in 1:(nrow(X))){ v <- sweep(u,2,X[i,],"+") %>% apply(1,paste,collapse=",")%in%XX if(identical(v,c(F,F,F))|identical(v,c(T,T,F))|identical(v,c(F,F,T))){tot <- tot+1} v <- sweep(u1,2,X[i,],"+") %>% apply(1,paste,collapse=",")%in%XX if(identical(v,c(F,F,F))|identical(v,c(T,T,F))|identical(v,c(F,F,T))){tot <- tot+1} v <- sweep(u2,2,X[i,],"+") %>% apply(1,paste,collapse=",")%in%XX if(identical(v,c(F,F,F))|identical(v,c(T,T,F))|identical(v,c(F,F,T))){tot <- tot+1} v <- sweep(u3,2,X[i,],"+") %>% apply(1,paste,collapse=",")%in%XX if(identical(v,c(F,F,F))|identical(v,c(T,T,F))|identical(v,c(F,F,T))){tot <- tot+1} } tot1 <- tot1+d12$csize[j]*tot } tot1
December 13, 2024 at 1:04 PM
johnprowle.bsky.social
A recursive function going backwards from the target number - not very pretty but takes about 400ms.
#Part 2 - does not rely on Part 1 solution as speed is sufficient dy7 <- function(target,nums){ if (length(nums)==1){ if(nums==target){return(T)} else{return(F)} } if(str_ends(target,as.character(nums[1]))==T&!target==nums[1]){ new <- as.numeric(str_trunc(target,width=(nchar(target)-nchar(nums[1])),side="right",ellipsis="")) if(new==nums[2]&length(nums)==2){return(T)} else{ res <- dy7(new,nums[-1]) if(res==T){return(res)} } } if(target/nums[1]>0&target%%nums[1]==0){ if(target/nums[1]==nums[2] & length(nums)==2){return(T)} res <- dy7(target/nums[1],nums[-1]) if(res==T){return(res)} } if(target-nums[1]>0){ res <- dy7(target-nums[1],nums[-1]) if(res==T){return(res)} } return(F) } d24.7<-aoc_get_response(7, session_cookie ) %>% content(encoding = 'UTF-8') %>%read_lines() %>% str_split(": ",simplify=T) d7.1 <- as.numeric(d24.7[,1]) d7.2 <- d24.7[,2] %>% str_split(" ") %>% lapply(rev) %>% lapply(as.numeric) tot1=0 tt=Sys.time() for(i in seq(d7.1)){ tot1=tot1+dy7(d7.1[i],d7.2[[i]])*d7.1[i] } format(tot1,scientific = F) Sys.time()-tt
December 7, 2024 at 11:49 PM