R/towerOfHanoi.R

In fun: Use R for Fun

towerOfHanoi <- function(n) {
    tower <- list(1:n, NULL, NULL)
    color <- rainbow(n)
    bgcolor <- par("bg")
    if (bgcolor == "transparent") 
        bgcolor <- "white"
    
    draw.hanoi <- function() {
        for (i in 1:3) {
            screen(i)
            plot(c(-n, n), c(0, n + 2), type = "n", xlab = "", 
                ylab = "")
            rect(-n, 0, n, n + 2, border = bgcolor, col = bgcolor)
            if (length(tower[[i]]) > 0) {
                barplot(rev(tower[[i]]), add = TRUE, horiz = TRUE, 
                  col = color[rev(tower[[i]])])
                barplot(-rev(tower[[i]]), add = TRUE, horiz = TRUE, 
                  col = color[rev(tower[[i]])])
            }
        }
    }
    
    move.hanoi <- function(k, from, to, via) {
        if (k > 1) {
            move.hanoi(k - 1, from, via, to)
            move.hanoi(1, from, to, via)
            move.hanoi(k - 1, via, to, from)
        }
        else {
            cat("Move ", tower[[from]][1], " from ", LETTERS[from], 
                " to ", LETTERS[to], "\n")
            tower[[to]] <<- c(tower[[from]][1], tower[[to]])
            tower[[from]] <<- tower[[from]][-1]
            draw.hanoi()
            Sys.sleep(0.5)
        }
    }
    
    close.screen(all = TRUE)
    split.screen(c(1, 3))
    
    draw.hanoi()
    move.hanoi(n, 1, 2, 3)
}