手写题目4：快速获取数组中最大的三项

快速获取数组中最大的三项

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转换那么多本质上还是排序，这里快速编写常见的排序算法

1. sort

var arr = [123, 3, 12, 14, 2, 45, 1, 5, 7, 2, 10]
var result = arr.sort((a, b) => { return a - b })

console.log(result.slice(-3))

2. 冒泡

var arr = [123, 3, 12, 14, 2, 45, 1, 5, 7, 2, 10]


function bolo(array) {

  for (let i = 0; i < array.length - 1; i++) {

    for (let j = 0; j < array.length - i - 1; j++) {
      if (array[j] > array[j + 1]) {
        let temp = array[j]
        array[j] = array[j + 1]
        array[j + 1] = temp
      }
    }

  }

  return array
}

console.log(bolo(arr).slice(-3))

3. 快排

var arr = [123, 3, 12, 14, 2, 45, 1, 5, 7, 2, 10]

function quickSort(array) {
  if (array.length <= 1) {
    return array
  }
  var left = []
  var right = []
  var centerIndex = Math.floor(array.length / 2)
  var centerElement = array.splice(centerIndex, 1)[0]

  for (let index = 0; index < array.length; index++) {
    const element = array[index];
    if (element < centerElement) {
      left.push(element)
    } else {
      right.push(element)
    }
  }

  return quickSort(left).concat([centerElement], quickSort(right))

}

console.log(quickSort(arr))