排序算法

冒泡排序

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

插入排序

function insertSort(arr){
    let len = arr.length;
    for(let i = 0; i < len; i++){
       let j = i;
       while (j>0){
           if(arr[j]<arr[j-1]){
               swap(arr,j,j-1);
               j--;
           }else{
               break;
           }
       }
    }
    return arr; 
}
function swap(arr,a,b){
    let tmp = arr[a];
    arr[a] = arr[b];
    arr[b] = tmp;
}

归并排序

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


function mergeSortRecursive(arr){
    if(arr.length === 1){
        return arr;
    }
    let mid = arr.length/2
    let leftArr = arr.slice(0,mid);
    let rightArr = arr.slice(mid,arr.length);
    return mergeSort(mergeSortRecursive(leftArr),mergeSortRecursive(rightArr));
}

快速排序

function quickSort(arr,l,r){
    if (l < r) {
        let i = l,j = r;
        let tmp = arr[i];
        while(i < j){
            while(i < j && arr[j] > tmp){
                --j;
            }
            arr[i] = arr[j];
            while (i < j && arr[i] <= tmp){ //=是必须的
                ++i;
            }
            arr[j] = arr[i]
        }
        arr[i] = tmp;
        quickSort(arr, l, i-1)  //quickSort(arr, 0, i-1)不能写为0，否则很慢
        quickSort(arr, i+1, r)
    }
}

希尔排序

function ShellSort(arr){
    let len = arr.length
    let gap = Math.floor(len / 2);
    while (gap>0){
        for (let i = gap; i < len; i++){
            let j = i;
            while (j-gap>=0&&arr[j]<arr[j-gap]){
                swap(arr,j,j-gap)
                j=j-gap
            }
        }
        gap=Math.floor(gap / 2)
   }
}