Coming late to the party, but I think this is gonna rock your world:

unique(cummax(sample.int(100)))

This uses a while loop and is wrapped in a function

# from ?sampleresample <- function(x, ...) x[sample.int(length(x), ...)]sample_z <-  function(n){  z <- numeric(n)  new <- 0  count <- 1  while(new < n){    from <- seq(new+1,n,by=1)    new <- resample(from, size= 1)    z[count] <- new    if(new < n)  count <- count+1  }  z[1:count]}set.seed(1234)sample_z(100)## [1]  12  67  88  96 100

Edit

note the change to deal with when the new sample is 100 and the way sample deals with an integer as opposed to a vector for x

Edit 2

Actually reading the help for sample gave the useful resample function. Which avoids the pitfalls when length(x) == 1

Not particularly efficient but:

X <- 0samps <- c()while (X < 100) {    if(is.null(samps)) {z <- 1 } else {z <- 1 + samps[length(samps)]}    if (z == 100) {        samps <- c(samps, z)    } else {         samps <- c(samps, sample(z:100, 1))    }    X <- samps[length(samps)]}

sampsEDIT: Trimming a little fat from it:

samps <- c()while (is.null(samps[length(samps)]) ||  samps[length(samps)] < 100 ) {    if(is.null(samps)) {z <- 1 } else {z <- 1 + samps[length(samps)]}    if (z == 100) {        samps <- c(samps, z)    } else {         samps <- c(samps, sample(z:100, 1))    }}samps