(算法)排序复习
选择排序
原理: 当i=0,首先找到最小的元素放在起始的位置,然后i=1,再然后找到最小的元素放到最左i=1的位置,然后i=2,...
动画演示
const SelectSort = arr => {
if (arr == null || arr.length < 2) {
return
}
for (let i = 0; i < arr.length-1; i++) {
let minIndex = i
for (let j = i + 1; j < arr.length; j++) {
if (arr[j] < arr[minIndex]) {
minIndex=j
}
}
if (minIndex !== i) {
swap(arr, i, minIndex)
}
}
return arr
}
const swap = (arr, i, j) => {
arr[i] = arr[i] ^ arr[j]
arr[j] = arr[i] ^ arr[j]
arr[i] = arr[i] ^ arr[j]
}
let arr = [1, 2, 10, 3, 4, 5, 6]
console.log(SelectSort(arr))
插入排序
const InsertSort = arr => {
if (arr == null || arr.length < 2) {
return
}
for (let i = 1; i < arr.length; i++) {
for (let j = i-1;j>=0&&arr[j]>arr[j+1];j--) {
swap(arr,j,j+1)
}
}
return arr
}
const swap = (arr, i, j) => {
arr[i] = arr[i] ^ arr[j]
arr[j] = arr[i] ^ arr[j]
arr[i] = arr[i] ^ arr[j]
}
let arr = [1, 2, 10, 3, 4, 5, 6]
console.log(InsertSort(arr))
归并排序
动画
逻辑解释
首先,讲数字分割成两份区域,在讲数字分割成两份区域,只到每块区域只有一个元素(这个过程是递归过程)
const mergeSort=array=>{ if(array.length<2) return array; let mid = Math.floor(array.length / 2) let left = array.slice(0, mid); let right = array.slice(mid); return merge(mergeSort(left), mergeSort(right)) } 举例说明入栈 [9, 3,4,5, 10,9, 6, 4] [9, 3,4,5] | [10,9,6, 4] [9,3] | [4,5] | [10,9] | [6,4] [9] [3]|[4] [5] |[10][9] | [6] [4]
截下来,讲分割的每块区域进行合并组合
[9] [3]|[4] [5] |[10][9] | [6] [4] 出栈 [3,9]|[4,5] |[9,10]|[4,6] [3,4][5,9] [3,4,5,9] | [4,6,9,10] //left[0]<arr[0] const merge=(left,right)=>{ let result=[]; while (left.length > 0 && right.length > 0) { if (left[0] < right[0]) { result.push(left.shift()) }else{ result.push(right.shift()) } } /*把长度不一样的连接起来*/ return result.concat(left).concat(right) }
桶排序
计数排序
动画
逻辑
- 计算出数组中的最大值
- 建立最大值加一的数组且数组中每一个数为0
- 新的数组进行值得累积
- 下面的打下断点就懂了
const bucketSort = arr => { if (arr == null || arr.length < 2) { return arr } let max = Math.max(...arr) let bucket = Array.from({length: max + 1}, v => 0) let oArr = [] for (let i = 0; i < arr.length; i++) { //值得累积 bucket[arr[i]]++ } for (let i = 0; i < bucket.length; i++) { while (bucket[i]-- > 0) { oArr.push(i) } } return oArr } console.log(bucketSort([10, 9, 7, 6, 3]))
基数排序
动画
//获取每位的数字位数 const getDigit = (x, d) => { let a = Math.pow(10, d) return Math.floor(x / a) % 10 } const radixSort=(arr)=> { //最大位数 let maxDigit = String(Math.max(...arr)).length let counter = [] for (let i = 0; i < maxDigit; i++) { for (let j = 0; j < arr.length; j++) { let bucket = getDigit(arr[j], i) if (counter[bucket] == null) { counter[bucket] = [] } counter[bucket].push(arr[j]) } let pos = 0 for (let j = 0; j < counter.length; j++) { let value = null if (counter[j] != null) { while ((value = counter[j].shift()) != null) { arr[pos++] = value } } } } return arr } let arr = [3, 44, 38, 5, 47, 15, 36, 26, 27, 2, 46, 4, 19, 50, 48] console.log(radixSort(arr, 2)) //[2, 3, 4, 5, 15, 19, 26, 27, 36, 38, 44, 46, 47, 48, 50]
自己修改版(不知道会不会写错,因为我自己写错了,所以还是改成前端看起来比较顺眼的)
//获取每位的数字位数 const getDigit = (x, d) => { let a = Math.pow(10, d) return Math.floor(x / a) % 10 } const radixSort = (arr) => { let maxDigit = String(Math.max(...arr)).length let counter = Array.from({length: 10}, () => []) for (let i = 0; i < maxDigit; i++) { for (let j = 0; j < arr.length; j++) { let a = getDigit(arr[j], i) counter[a].push(arr[j]) } let b=0; counter.forEach(val=>{ while (val.length > 0) { arr[b++]=val.shift() } }) } return arr } let arr = [3, 44, 38, 5, 47, 15, 36, 26, 27, 2, 46, 4, 19, 50, 48] console.log(radixSort(arr)) //[2, 3, 4, 5, 15, 19, 26, 27, 36, 38, 44, 46, 47, 48, 50]
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