# JS模拟排序算法和搜索算法

Typescript版本的排序和搜索算法

# 排序算法

## 算法中用到的公共函数

``````const Compare = {
LESS_THAN: -1,
BIGGER_THAN: 1,
EQUALS: 0
};

const DOES_NOT_EXIST = -1;

function lesserEquals(a, b, compareFn) {
const comp = compareFn(a, b);
return comp === Compare.LESS_THAN || comp === Compare.EQUALS;
}

function biggerEquals(a, b, compareFn) {
const comp = compareFn(a, b);
return comp === Compare.BIGGER_THAN || comp === Compare.EQUALS;
}

function defaultCompare(a, b) {
if (a === b) {
return Compare.EQUALS;
}
return a < b ? Compare.LESS_THAN : Compare.BIGGER_THAN;
}

function defaultEquals(a, b) {
return a === b;
}

function defaultToString(item) {
if (item === null) {
return 'NULL';
} else if (item === undefined) {
return 'UNDEFINED';
} else if (typeof item === 'string' || item instanceof String) {
return `\${item}`;
}
return item.toString();
}

function swap(array, a, b) {
[array[a], array[b]] = [array[b], array[a]];
}
function reverseCompare(compareFn) {
return (a, b) => compareFn(b, a);
}

function defaultDiff(a, b) {
return Number(a) - Number(b);
}``````

## 冒泡排序

``````function bubbleSort(array, compareFn = defaultCompare) {
const { length } = array;
for (let i = 0; i < length; i++) {
// console.log('--- ');
for (let j = 0; j < length - 1; j++) {
// console.log('compare ' + array[j] + ' with ' + array[j + 1]);
if (compareFn(array[j], array[j + 1]) === Compare.BIGGER_THAN) {
// console.log('swap ' + array[j] + ' with ' + array[j + 1]);
swap(array, j, j + 1);
}
}
}
return array;
}``````

## 改进的冒泡排序(减少中间比较)

``````function modifiedBubbleSort(array, compareFn = defaultCompare) {
const { length } = array;
for (let i = 0; i < length; i++) {
// console.log('--- ');
for (let j = 0; j < length - 1 - i; j++) {
// console.log('compare ' + array[j] + ' with ' + array[j + 1]);
if (compareFn(array[j], array[j + 1]) === Compare.BIGGER_THAN) {
// console.log('swap ' + array[j] + ' with ' + array[j + 1]);
swap(array, j, j + 1);
}
}
}
return array;
}``````

## 选择排序

``````function selectionSort (array, compareFn = defaultCompare) => {
const { length } = array;
let indexMin;
for (let i = 0; i < length - 1; i++) {
indexMin = i;
// console.log('index ' + array[i]);
for (let j = i; j < length; j++) {
if (compareFn(array[indexMin], array[j]) === Compare.BIGGER_THAN) {
// console.log('new index min ' + array[j]);
indexMin = j;
}
}
if (i !== indexMin) {
// console.log('swap ' + array[i] + ' with ' + array[indexMin]);
swap(array, i, indexMin);
}
}
return array;
};``````

## 插入排序

``````function insertionSort (array, compareFn = defaultCompare) => {
const { length } = array;
let temp;
for (let i = 1; i < length; i++) {
let j = i;
temp = array[i];
// console.log('to be inserted ' + temp);
while (j > 0 && compareFn(array[j - 1], temp) === Compare.BIGGER_THAN) {
// console.log('shift ' + array[j - 1]);
array[j] = array[j - 1];
j--;
}
// console.log('insert ' + temp);
array[j] = temp;
}
return array;
};``````

## 归并排序

``````function merge(left, right, compareFn) {
let i = 0;
let j = 0;
const result = [];
while (i < left.length && j < right.length) {
result.push(compareFn(left[i], right[j]) === Compare.LESS_THAN ? left[i++] : right[j++]);
}
return result.concat(i < left.length ? left.slice(i) : right.slice(j));
}
function mergeSort(array, compareFn = defaultCompare) {
if (array.length > 1) {
const { length } = array;
const middle = Math.floor(length / 2);
const left = mergeSort(array.slice(0, middle), compareFn);
const right = mergeSort(array.slice(middle, length), compareFn);
array = merge(left, right, compareFn);
}
return array;
}``````

## 快速排序

`````` // 划分过程
function partition(array, left, right, compareFn) {
const pivot = array[Math.floor((right + left) / 2)];
let i = left;
let j = right;

while (i <= j) {
while (compareFn(array[i], pivot) === Compare.LESS_THAN) {
i++;
}
while (compareFn(array[j], pivot) === Compare.BIGGER_THAN) {
j--;
}
if (i <= j) {
swap(array, i, j);
i++;
j--;
}
}
return i;
}
function quick(array, left, right, compareFn) {
let index;
if (array.length > 1) {
index = partition(array, left, right, compareFn);
if (left < index - 1) {
quick(array, left, index - 1, compareFn);
}
if (index < right) {
quick(array, index, right, compareFn);
}
}
return array;
}
function quickSort(array, compareFn = defaultCompare) {
return quick(array, 0, array.length - 1, compareFn);
}``````

## 计数排序

``````function countingSort(array) {
if (array.length < 2) {
return array;
}
const maxValue = findMaxValue(array);
let sortedIndex = 0;
const counts = new Array(maxValue + 1);
array.forEach(element => {
if (!counts[element]) {
counts[element] = 0;
}
counts[element]++;
});
// console.log('Frequencies: ' + counts.join());
counts.forEach((element, i) => {
while (element > 0) {
array[sortedIndex++] = i;
element--;
}
});
return array;
}``````

## 桶排序

``````// 引入前面的插入排序
import { insertionSort } from './insertion-sort';

function createBuckets(array, bucketSize) {
let minValue = array[0];
let maxValue = array[0];
for (let i = 1; i < array.length; i++) {
if (array[i] < minValue) {
minValue = array[i];
} else if (array[i] > maxValue) {
maxValue = array[i];
}
}
const bucketCount = Math.floor((maxValue - minValue) / bucketSize) + 1;
const buckets = [];
for (let i = 0; i < bucketCount; i++) {
buckets[i] = [];
}
for (let i = 0; i < array.length; i++) {
buckets[Math.floor((array[i] - minValue) / bucketSize)].push(array[i]);
}
return buckets;
}
function sortBuckets(buckets) {
const sortedArray = [];
for (let i = 0; i < buckets.length; i++) {
if (buckets[i] != null) {
insertionSort(buckets[i]);
sortedArray.push(...buckets[i]);
}
}
return sortedArray;
}
function bucketSort(array, bucketSize = 5) {
if (array.length < 2) {
return array;
}
const buckets = createBuckets(array, bucketSize);
return sortBuckets(buckets);
}``````

## 基数排序

``````function findMaxValue(array, compareFn = defaultCompare) {
if (array && array.length > 0) {
let max = array[0];
for (let i = 1; i < array.length; i++) {
if (compareFn(max, array[i]) === Compare.LESS_THAN) {
max = array[i];
}
}
return max;
}
return undefined;
}
function findMinValue(array, compareFn = defaultCompare) {
if (array && array.length > 0) {
let min = array[0];
for (let i = 1; i < array.length; i++) {
if (compareFn(min, array[i]) === Compare.BIGGER_THAN) {
min = array[i];
}
}
return min;
}
return undefined;
}

const getBucketIndex = (value, minValue, significantDigit, radixBase) =>
Math.floor(((value - minValue) / significantDigit) % radixBase);

let bucketsIndex;
const buckets = [];
const aux = [];
for (let i = 0; i < radixBase; i++) {
buckets[i] = 0;
}
for (let i = 0; i < array.length; i++) {
bucketsIndex = getBucketIndex(array[i], minValue, significantDigit, radixBase);
buckets[bucketsIndex]++;
}
for (let i = 1; i < radixBase; i++) {
buckets[i] += buckets[i - 1];
}
for (let i = array.length - 1; i >= 0; i--) {
bucketsIndex = getBucketIndex(array[i], minValue, significantDigit, radixBase);
aux[--buckets[bucketsIndex]] = array[i];
}
for (let i = 0; i < array.length; i++) {
array[i] = aux[i];
}
return array;
};
if (array.length < 2) {
return array;
}
const minValue = findMinValue(array);
const maxValue = findMaxValue(array);
// Perform counting sort for each significant digit, starting at 1
let significantDigit = 1;
while ((maxValue - minValue) / significantDigit >= 1) {
}
return array;
}``````

# 搜索算法

## 顺序搜索

``````function sequentialSearch(array, value, equalsFn = defaultEquals) {
for (let i = 0; i < array.length; i++) {
if (equalsFn(value, array[i])) {
return i;
}
}
return DOES_NOT_EXIST;
}``````

## 二分搜索

``````// 引入文章前面的快速排序方法
import { quickSort } from 'quicksort';

function binarySearch(array, value, compareFn = defaultCompare) {
const sortedArray = quickSort(array);
let low = 0;
let high = sortedArray.length - 1;
while (low <= high) {
const mid = Math.floor((low + high) / 2);
const element = sortedArray[mid];
// console.log('mid element is ' + element);
if (compareFn(element, value) === Compare.LESS_THAN) {
low = mid + 1;
// console.log('low is ' + low);
} else if (compareFn(element, value) === Compare.BIGGER_THAN) {
high = mid - 1;
// console.log('high is ' + high);
} else {
// console.log('found it');
return mid;
}
}
return DOES_NOT_EXIST;
}``````

## 内插搜索

``````// 引入前面的工具函数和相关变量
import {
biggerEquals,
Compare,
defaultCompare,
defaultEquals,
defaultDiff,
DOES_NOT_EXIST,
lesserEquals
} from '../../util';

function interpolationSearch(
array,
value,
compareFn = defaultCompare,
equalsFn = defaultEquals,
diffFn = defaultDiff
) {
const { length } = array;
let low = 0;
let high = length - 1;
let position = -1;
let delta = -1;
while (
low <= high &&
biggerEquals(value, array[low], compareFn) &&
lesserEquals(value, array[high], compareFn)
) {
delta = diffFn(value, array[low]) / diffFn(array[high], array[low]);
position = low + Math.floor((high - low) * delta);
if (equalsFn(array[position], value)) {
return position;
}
if (compareFn(array[position], value) === Compare.LESS_THAN) {
low = position + 1;
} else {
high = position - 1;
}
}
return DOES_NOT_EXIST;
}``````

## 随机算法Fisher—Yates(洗扑克牌)

``````function shuffle(array) {
for(let i=array.length;i>0;i--) {
const randomIndex = Math.floor(Math.random()*(i+1));
swap(array, i, randomIndex);
}
return array;
}``````