consecutive-sums.js

#!/usr/local/bin/node



//////////////////
// Combinations //
//////////////////

// build all consecutive combination of elements, given an array
function getConsecutiveCombinations(orig_arr) {
  var combinations = []

  for (var pointer = 0; pointer <= orig_arr.length; pointer++) {
    for (var size = pointer; size <= orig_arr.length; size++) {
      var new_arr = orig_arr.slice(pointer, size)
      if ( new_arr.length > 0 ) {
        combinations.push(new_arr)
      }
    }
  }

  return combinations
}

// add the above to `Array.prototype`,
// so that we can call it as a method, like...
//
// [1,2].getConsecutiveCombinations()
Array.prototype.getConsecutiveCombinations = function() {
  return getConsecutiveCombinations(this)
}



/////////////
// Helpers //
/////////////

// sum all numbers in an array (imperative `+=` approach)
function sum(arr) {
  var total = 0

  arr.forEach(function(num) { total += num })

  return total
}
// // sum all numbers in an array (functional (`reduce`) approach)
//
// function sum(arr) {
//   return arr.reduce(function(total, num) {
//     return total + num
//   })
// }


// function to sort numbers sanely
// (instead of using implicit `toString`)
function sortNumbers(x,y) { return x - y }


// helper method to get the last element of an array
Array.prototype.last = function() { return this[this.length - 1] }



//////////////
// Run it!  //
//////////////

// calculate and print our max
var numbers = [-5, 10, 2, -3, 5, 8, -20]
var max =
  numbers
    .getConsecutiveCombinations()
    .map(sum)
    .sort(sortNumbers)
    .last()

console.log(max)


// // `max` above could also be defined as...
// var max = numbers.getConsecutiveCombinations().map(toSum).sort(sortNumbers).last()

searches

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