(This article was first published on

**The Research Kitchen Weblog » R**, and kindly contributed to R-bloggers)Problem 14 on the Project Euler site asks us to find the longest chain under 1 million created using the Collatz mapping. This is fairly straightforward, although performance again is not great: ## Problem 14 # Collatz conjecture problem14 <- function(N) { maxChain <- 0 chains <- rep(0,N) x <- 1 for (i in 1:N) { n <- i chain <- 0 while(n > 1) { n <- ifelse(n %% 2 == 0, n/2, 3*n+1) chain <- chain + 1 if (n < N && chains[n] > […]

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