Comments (2)
冒泡排序 bubbleSort
基本算法
最基本的排序算法, 比较排序, 理论时间复杂度O( n^2 )
// compare times, swap times, sort result
// 153, 29, [ 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 15, 18, 22, 30, 39, 44, 95 ]
function bubbleSort(data) {
function swap(arr, i, j) {
[arr[j], arr[i]] = [arr[i], arr[j]];
}
for (let i = data.length - 1; i > 0; i = --i) {
for (let j = 0; j < i; j++) {
if (data[j] > data[j + 1]) {
swap(data, j, j + 1);
}
}
}
return data;
}
优化算法
1. 提前结束--有事奏来, 无事退朝
本例中, 添加flag标志, 用于提前结束排序, 算是一种改进
// compare times, swap times, sort result
// 62, 29, [ 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 15, 18, 22, 30, 39, 44, 95 ]
function bubbleSort(data) {
function swap(arr, i, j) {
[arr[j], arr[i]] = [arr[i], arr[j]];
}
let flag; // 内层循环没有交换, 说明已达到有序
for (let i = data.length - 1; i > 0; --i) {
flag = true;
for (let j = 0; j < i; j++) {
cnt++;
if (data[j] > data[j + 1]) {
flag = false;
swap(data, j, j + 1);
}
}
if (flag) {
return data;
}
}
return data;
}
2. 未动归档
当序列中, 局部有序时, 可以忽略这一部分的对比, 通过在内层循记住最后一次交换次序位置, 外层即可直接把该位置作为已排好序的部分来"归档"
// compare times, swap times, sort result
// 52, 29, [ 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 15, 18, 22, 30, 39, 44, 95 ]
function bubbleSort(data) {
function swap(arr, i, j) {
[arr[j], arr[i]] = [arr[i], arr[j]];
}
let prePos = data.length - 1;
for (let i = prePos; i > 0; i = prePos || i - 1) {
prePos = false;
for (let j = 0; j < i; j++) {
if (data[j] > data[j + 1]) {
prePos = j + 1
swap(data, j, prePos);
}
}
}
return data;
}
双向遍历, 从左到右+从右到左交替遍历, 每次确定1个最大和1个最小
综合利用1, 2两种优化
// compare times, swap times, sort result
// 46, 29, [ 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 15, 18, 22, 30, 39, 44, 95 ]
function bubbleSort(data) {
function swap(arr, i, j) {
[arr[j], arr[i]] = [arr[i], arr[j]];
}
let prePos = data.length - 1;
let flag;
for (let i = prePos; i > 0; i = prePos || i - 1) {
flag = true;
prePos = false;
for (let j = 0; j < i; j++) {
if (data[j] > data[j + 1]) {
flag = false;
prePos = j + 1
swap(data, j, prePos);
}
}
if (flag) {
return data;
}
}
return data;
}
综合利用 2,3 种优化
// 108 29 [ 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 15, 18, 22, 30, 39, 44, 95 ]
function bubbleSort(data) {
function swap(arr, x, y) {
[arr[x], arr[y]] = [arr[y], arr[x]];
}
let l2r = 0, r2l = data.length - 1;
let flat = true;
while (l2r < r2l) {
for (let i = l2r; i < r2l; i++) {
if (data[i] > data[i + 1]) {
swap(data, i, i + 1);
flag = false;
}
}
r2l--;
for (let j = r2l; j > l2r; j--) {
if (data[j - 1] > data[j]) {
swap(data, j, j - 1);
flag = false;
}
}
l2r++;
if (flag) {
break;
}
flag = true;
}
return data;
}
综合1,2,3种优化
// 71 29 [ 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 15, 18, 22, 30, 39, 44, 95 ]
function bubbleSort(data) {
function swap(arr, x, y) {
[arr[x], arr[y]] = [arr[y], arr[x]];
}
let l2r = 0, r2l = data.length - 1;
let flag;
let l2rPos = false, r2lPos = false;
while(l2r < r2l) {
flag = true;
for(let i = l2r; i < r2l; i ++){
if(data[i] > data[i+1]) {
flag = false;
swap(data, i, i + 1);
l2rPos = i + 1
}
}
r2l = l2rPos || r2l - 1;
l2rPos = false;
for(let j = r2l - 1; j > l2r; j--) {
if(data[j-1] > data[j]) {
swap(data, j, j - 1);
r2lPos = j - 1
}
}
l2r = r2lPos || l2r + 1;
rl2Pos = false;
}
return data;
}
具体测试用例之后再来补充
from blog.
选择排序 selectionSort
最基本的排序算法之一, 选择排序, 理论O( n^2 )
基本算法
简单选择排序
每次循环得到一个最值
双端选择排序
每次循环定位一大一小两个最值
from blog.
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