【S3-E427】javascript 算法整理

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快速排序

function quickSort(ary, isDesc) {
var len = ary.length;
if (len < 3) {
return ary;
}
var baseIndex = Math.floor(len / 2),
base = ary[baseIndex];
var smallAry = [],
largeAry = [];
for (var i = len - 1, cur; i > -1; i--) {
cur = ary[i];
if (i == baseIndex) {
continue;
}
if (isDesc) {
cur < base ? (largeAry[largeAry.length] = cur) : (smallAry[smallAry.length] = cur);
} else {
cur >= base ? (largeAry[largeAry.length] = cur) : (smallAry[smallAry.length] = cur);
}
}
smallAry[smallAry.length] = base;
return quickSort(smallAry, isDesc).concat(quickSort(largeAry, isDesc));
}

function halfSearch(ary, num) {
var len = ary.length,
middle = Math.floor(len / 2),
midNum = ary[middle];
if (len == 0) {
return null;
} else if (num === midNum) {
return midNum;
} else if (midNum > num ) {
return halfSearch(ary.slice(0, middle), num);
} else {
return halfSearch(ary.slice(middle + 1), num);
}
}

var testAry = [9, 2, 3, 4, 1, 0, 8, 4, 2];
var sortedAry = quickSort(testAry);
console.log(sortedAry, "快速排序");
console.log(testAry, "原始数组");
console.log(halfSearch(sortedAry, 3), "二分查找");

冒泡排序

var common = require('./common');

function bubbleSort(ary){
console.time('冒泡排序耗时');
var len = ary.length;
for(var i = 0; i < len; i++){
for(var j = 0; j < len-1-i; j++){
if(ary[j] > ary[j+1]){
var tmp = ary[j];
ary[j] = ary[j+1];
ary[j+1] = tmp;
}
}
}
console.timeEnd('冒泡排序耗时');
return ary;
}

function bubbleSort2(ary){
console.time('改进后的冒泡排序耗时');
var i = ary.length -1;
while(i > 0){
var pos;
for(var j = 0; j < i; j++){
if(ary[j] > ary[j+1]){
pos = j;
var tmp = ary[j];
ary[j] = ary[j+1];
ary[j+1] = tmp;
}
i = pos;
}
}
console.timeEnd('改进后的冒泡排序耗时');
return ary;
}

var ary = common.createAry(200);
console.log("排序前", ary.toString());
var result = bubbleSort(ary);
console.log(result.toString(), "冒泡排序后");
console.log(tmp.toString());
result = bubbleSort2(tmp);
console.log(result.toString(), "改进的冒泡排序后");

选择排序

var common = require('./common');
function chooseSort(ary){
console.time("选择排序耗时");
var len = ary.length,
tmp, minIndex;
for(var i = 0; i < len; i++){
minIndex = i;
for(j = i+1; j < len - i; j++){
if(ary[j] < ary[minIndex]){
minIndex = j;
}
}
tmp = ary[i];
ary[i] = ary[minIndex];
ary[minIndex] = tmp;
}
console.timeEnd('选择排序耗时');
return ary;
}

var ary = common.createAry(20);
console.log('排序前', ary);
var sortedAry = chooseSort(ary);
console.log('排序后', sortedAry);

插入排序

var common = require('./common');
function insertSort(ary) {
console.time('插入排序耗时');
var len = ary.length;
for (var i = 1; i < len; i++) {
var key = ary[i],
j = i - 1;
while (j >= 0 && key < ary[j]) {
ary[j + 1] = ary[j];
j--;
}
ary[j + 1] = key;
}
console.timeEnd('插入排序耗时');
return ary;
}

var ary = common.createAry(20);
console.log('排序前', ary);
var sortedAry = insertSort(ary);
console.log('排序后', sortedAry);
common.js

exports.createAry = function(number){
var ary = [];
for(let i = 0; i < number; i++){
ary.push(Math.floor(Math.random()*100));
}
return ary;
}

转自：https://segmentfault.com/a/1190000011195531
作者： gristar

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