js十大經典算法排序

visualgo算法排序可視化：https://visualgo.net/zh/

一、冒泡排序。

/**
 * 冒泡排序
 * @param {Array} arr - 數組
 * @returns {Array} - 排序好的數組
 */
 console.time('冒泡排序')
function bubbleSort(arr) {
    let len = arr.length;
    let temp;
    for (let i = 0; i < len; i++) {
        for (let j = 0; j < len - 1 - i; j++) {
        	// 如果後邊的比較小，和前面的換下位置。
            if (arr[j] > arr[j + 1]) {
                temp = arr[j + 1];
                arr[j + 1] = arr[j];
                arr[j] = temp
            }
        }
    }
    return arr
}
let arr = [1, 2, 234, 235, 23452, 234525, 4, 2, 5]
console.log(bubbleSort(arr))
console.timeEnd('冒泡排序')

二、選擇排序。

/**
 * 選擇排序
 * @param {Array} arr - 數組
 * @returns {Array} - 排序好的數組
 */

console.time('選擇排序')

function selectionSort(arr) {
    let len = arr.length;
    let temp, minIndex;
    for (let i = 0; i < len - 1; i++) {
        minIndex = i
        for (let j = i + 1; j < len; j++) {
            if (arr[j] < arr[minIndex]) {
                minIndex = j
            }
        }
        temp = arr[i];
        arr[i] = arr[minIndex];
        arr[minIndex] = temp
    }
    return arr
}
let arr = [1, 2, 234, 235, 23452, 234525, 4, 2, 5]
console.log(selectionSort(arr))
console.timeEnd('選擇排序')

三、插入排序。

/**
 * 插入排序
 * @param {Array} arr
 * @returns {Array}
 */

console.time('插入排序')

function insertionSort(arr) {
    let len = arr.length;
    let preIndex, current;
    for (let i = 1; i < len; i++) {
        preIndex = i - 1;
        current = arr[i]

        while (preIndex >= 0 && arr[preIndex] > current) {
            arr[preIndex + 1] = arr[preIndex]
            preIndex--;
        }
        arr[preIndex + 1] = current
    }
    return arr
}
let arr = [1, 2, 234, 235, 23452, 234525, 4, 2, 5]
console.log(insertionSort(arr))
console.timeEnd('插入排序')

四、希爾排序。

/**
 * 希爾排序,優化版的插入排序
 * @param {Array} arr
 * @returns {Array}
 */

console.time('希爾排序')

function shellSort(arr) {
    let len = arr.length;
    let temp, gap = 1;
    while (gap < len / 3) {
        gap = gap * 3 + 1;
    }
    for (gap; gap > 0; gap = Math.floor(gap / 3)) {
        for (let i = gap; i < len; i++) {
            temp = arr[i];
            for (var j = i - gap; j >= 0 && arr[j] > temp; j -= gap) {
                arr[j + gap] = arr[j]
            }
            arr[j + gap] = temp
        }
    }
    return arr
}
let arr = [1, 2, 234, 235, 23452, 234525, 4, 2, 5]
console.log(shellSort(arr))
console.timeEnd('希爾排序')

五、歸併排序

/**
 * 歸併排序
 * @param {Array} arr
 * @returns {Array}
 */

console.time('歸併排序')

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

function merge(left, right) {
    let result = [];
    while (left.length && right.length) {
        if (left[0] <= right[0]) {
            result.push(left.shift())
        } else {
            result.push(right.shift())
        }
    }
    while (left.length) {
        result.push(left.shift())
    }
    while (right.length) {
        result.push(right.shift())
    }
    return result
}


let arr = [1, 2, 234, 235, 23452, 234525, 4, 2, 5]
console.log(mergeSort(arr))
console.timeEnd('歸併排序')