knapsackLight.R

# You found two items in a treasure chest! The first item weighs weight1 and is
# worth value1, and the second item weighs weight2 and is worth value2. What is
# the total maximum value of the items you can take with you, assuming that your
# max weight capacity is maxW and you can't come back for the items later?
#
# Note that there are only two items and you can't bring more than one item of
# each type, i.e. you can't take two first items or two second items.
#
# Example
#
# For value1 = 10, weight1 = 5, value2 = 6, weight2 = 4, and maxW = 8, the
# output should be knapsackLight(value1, weight1, value2, weight2, maxW) = 10.
#
# You can only carry the first item.
#
# For value1 = 10, weight1 = 5, value2 = 6, weight2 = 4, and maxW = 9, the
# output should be knapsackLight(value1, weight1, value2, weight2, maxW) = 16.
#
# You're strong enough to take both of the items with you.
#
# For value1 = 5, weight1 = 3, value2 = 7, weight2 = 4, and maxW = 6, the output
# should be knapsackLight(value1, weight1, value2, weight2, maxW) = 7.
#
# You can't take both items, but you can take any of them.

knapsackLight <- function(value1, weight1, value2, weight2, maxW) {
  if (maxW >= (weight1 + weight2)) {
    return(value1 + value2)
  } else {
    if (weight1 > maxW && weight2 > maxW) {
      return(0)
    }
    if (weight1 <= maxW && weight2 <= maxW) {
      return(max(value1,value2))
    } else {
      if (weight1 <= maxW) {
        return(value1)
      } else {
        return(value2)
      }
    } 
  }
}

#more elegant solution
knapsackLight <- function(value1, weight1, value2, weight2, maxW) {
  return(max((weight1<=maxW)*value1,(weight2<=maxW)*value2,((weight1+weight2)<=maxW)*(value1+value2),0))
}