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// 冒泡排序
function bubbleSort(arr) {
    var len = arr.length;
    for(var i = 0; i < len - 1; i++) {
        for(var j = 0; j < len - 1 - i; j++) {
            if(arr[j] > arr[j+1]) {        // 相邻元素两两对比
                vartemp = arr[j+1];        // 元素交换
                arr[j+1] = arr[j];
                arr[j] = temp;
            }
        }
    }
    return arr;
}

function selectionSort(arr) {
    var len = arr.length;
    var minIndex, temp;
    for(var i = 0; i < len - 1; i++) {
        minIndex = i;
        for(var j = i + 1; j < len; j++) {
            if(arr[j] < arr[minIndex]) {     // 寻找最小的数
                minIndex = j;                 // 将最小数的索引保存
            }
        }
        temp = arr[i];
        arr[i] = arr[minIndex];
        arr[minIndex] = temp;
    }
    return arr;
} 

// 插入排序
function insertionSort(arr) {
    var len = arr.length;
    var preIndex, current;
    for(var 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;
}

function shellSort(arr) {
    var len = arr.length;
    for(var gap = Math.floor(len / 2); gap > 0; gap = Math.floor(gap / 2)) {
        for(vari = gap; i < len; i++) {
            var j = i;
            var current = arr[i];
            while(j - gap >= 0 && current < arr[j - gap]) {
                 arr[j] = arr[j - gap];
                 j = j - gap;
            }
            arr[j] = current;
        }
    }
    return arr;
}

function mergeSort(arr) {
    var len = arr.length;
    if(len < 2) {
        returnarr;
    }
    var middle = Math.floor(len / 2),
        left = arr.slice(0, middle),
        right = arr.slice(middle);
    return merge(mergeSort(left), mergeSort(right));
}
 
function merge(left, right) {
    var result = [];
 
    while(left.length>0 && right.length>0) {
        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());
 
    returnresult;
}

function quickSort(arr, left, right) {
    var len = arr.length,
        partitionIndex,
        left = typeofleft != 'number'? 0 : left,
        right = typeofright != 'number'? len - 1 : right;
 
    if(left < right) {
        partitionIndex = partition(arr, left, right);
        quickSort(arr, left, partitionIndex-1);
        quickSort(arr, partitionIndex+1, right);
    }
    return arr;
}
 
function partition(arr, left ,right) {     // 分区操作
    var pivot = left,                      // 设定基准值（pivot）
        index = pivot + 1;
    for(vari = index; i <= right; i++) {
        if(arr[i] < arr[pivot]) {
            swap(arr, i, index);
            index++;
        }       
    }
    swap(arr, pivot, index - 1);
    return index-1;
}
 
function swap(arr, i, j) {
    var temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}

// 计数排序
function countingSort(arr, maxValue) {
    var bucket = new Array(maxValue + 1),
        sortedIndex = 0;
        arrLen = arr.length,
        bucketLen = maxValue + 1;
 
    for(var i = 0; i < arrLen; i++) {
        if(!bucket[arr[i]]) {
            bucket[arr[i]] = 0;
        }
        bucket[arr[i]]++;
    }
 
    for(var j = 0; j < bucketLen; j++) {
        while(bucket[j] > 0) {
            arr[sortedIndex++] = j;
            bucket[j]--;
        }
    }
 
    returnarr;
}