reverse_string.R

reverse_string.R

s <- c("ab(dc)a")

reverseParentheses <- function(s) {
# split the string vector into character vectors
s <- strsplit(s, NULL)[[1]]

# recrusively call and operate on the character vector
for (i in seq_along(s)) {
  if (s[i] == "(") {
    begin <- i
  }
  if (s[i] == ")") {
    final <- i
    # create a new reverse 'string' segmenting,
    # collapsing, and reversing inner pairs
    # also removing parenthese by incrementing/decrementing
    rev.string <- paste(c(s[1:(begin - 1)],
                        rev(c(s[(begin + 1):(final - 1)])),
                        s[(final + 1):length(s)]),
                        sep = "",
                        collapse = "")
    # use recrusion to repeat on innermost parentheses
    rev.string <- reverseParentheses(rev.string)
    }
  }

    return(rev.string)
}

reverseParentheses(s)
# expecting "abcda"