排序总结

• 之前写的排序总结一遍. 大部分来源js算法那本书
• 还有一个堆排序没传, 那个可得细细的写

二分查找

function bianryList(arr, item) {
  var low = 0
  var heigh = arr.length - 1
  while (low <= heigh) {
    var mid = Math.floor((low + heigh)/2)
    var temp = arr[mid]
    if (temp === item) return mid
    if (temp > item) {
      heigh = mid - 1
    } else {
      low = mid + 1
    }
    debugger
  }
  return null
}

var arr = [1,2,3,5,6,9,12,15]
var res = bianryList(arr, 15)
debugger;

冒泡排序

function maopao(arra) {

  var temp;
  let count = 0
  for (var i = 0; i < arra.length-1; i++) { //比较多少趟，从第一趟开始

    for (var j = 0; j < arra.length - i - 1; j++) { //每一趟比较多少次数
      count++
      if (arra[j] > arra[j + 1]) {
        temp = arra[j];
        arra[j] = arra[j + 1];
        arra[j + 1] = temp;
      }
    }
  };
  console.log(count)
  return arra;
}

var arrry = [85, 24, 63, 17, 31, 17, 86, 50];

var s = maopao(arrry);
debugger

插入排序

function insertionSort(array) {
  var length = array.length,
    j, temp;
  for (var i = 1; i < length; i++) {
    j = i;
    temp = array[i];
    while (j > 0 && array[j - 1] > temp) {
      array[j] = array[j - 1];
      j--;
    }
    array[j] = temp;
  };
}

var arr = [3, 5, 1, 4, 2, 6]
insertionSort(arr)
debugger

归并排序

function mergeSort(arr) {
  var len = arr.length
  if (len < 2) {
    return arr
  }
  var mid = Math.floor(len / 2)
  var left = arr.slice(0, mid)
  var right = arr.slice(mid, len)
  return merge(mergeSort(left), mergeSort(right))
}

function merge(left, right) {
  var reslut = []
  var li = 0
  var ri = 0
  while (li < left.length && ri < right.length) {
    if (left[li] > right[ri]) {
      reslut.push(right[ri++])
    } else {
      reslut.push(left[li++])
    }
  }

  while (li < left.length) {
    reslut.push(left[li++])
  }
  while (ri < right.length) {
    reslut.push(right[ri++])
  }

  return reslut
}

var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
mergeSort(arr)
debugger

快速排序

function quickArr(arr) {
  var len = arr.length
  if (len < 2) {
    return arr
  }
  debugger
  var temp = arr[0]
  var left = []
  var right = []
  arr.forEach((val, index, arr) => {
    if (index === 0) {
      return
    }
    if (val < temp) {
      left.push(val)
    } else {
      right.push(val)
    }
  })
  // return Array.prototype.concat(quickArr(left), temp, quickArr(right))
  return quickArr(left).concat(temp, quickArr(right))
}

var arr = [1, 3, 4, 2, 5, 6]
var res = console.log(quickArr(arr))
console.log(arr)
debugger;