常见排序算法

冒泡排序

function bubbleSort (arr) {
    let length = arr.length
    for(let i = 0; i < length; i++) {
        for(let j = 0; j < length - i; j++) {
            if (arr[j] > arr[j + 1]) {
                [arr[j], arr[j + 1]] = [arr[j + 1], arr[j]]
            }
        }
    }
    return arr
}

选择排序

function selectSort (arr) {
    let length = arr.length
    for(let i = 0; i < length; i++) {
        for (let j = i + 1; j < length; j++) {
            if (arr[j] < arr[i]) {
                [arr[i], arr[j]] = [arr[j], arr[i]]
            }
        }
    }
    return arr
}

快速排序

function quickSort (arr) {
    if (arr.length <= 1) { return arr }
    let midIndex = Math.floor(arr.length / 2)
    let midValue = arr.splice(midIndex, 1)
    let left = []
    let right = []
    for (let i = 0; i< arr.length; i++) {
        arr[i] < midValue ? left.push(arr[i]) : right.push(arr[i])
    }
    return quickSort(left).concat(midValue, quickSort(right))
}

插入排序

function insertionSort(arr) {
    var length = arr.length;
    var preIndex, current;
    for(var i=1; i<length; 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;
}