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java - 为什么我的不同排序算法会导致相同的运行时间？

转载 作者：塔克拉玛干 更新时间：2023-11-03 05:36:28 24 4
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对于 CS 家庭作业，我将在 Java 中创建大小不断增加的随机数组，并将它们的运行时间绘制在图表上。但是，当使用相同的输入运行时，我的插入、合并和快速排序的实现似乎具有相同的运行时间。我已经多次以不同的方式实现它们，但仍然得到相同的结果。这是我的代码:

import java.util.*; import java.util.Random;

public class Complexity {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    Scanner input= new Scanner(System.in);
    System.out.println("Enter the array size: ");
    int a = input.nextInt(); 
    System.out.println("Enter the number size: ");
    int n = input.nextInt();

    int[] arr = newArr(a, n);
    int[] arr2 = arr.clone();
    int[] arr3 = arr.clone();

//INSERT SORT
    long startTime = System.nanoTime();
    insertSort(arr);
    long endTime = System.nanoTime();
    long duration = (endTime - startTime)/1000000;
    System.out.println("Insert Sort Time:" + duration + "ms");

//MERGE SORT
    long start = System.nanoTime();
    mergeSort(arr2, 0, a-1);
    long end = System.nanoTime();
    long dur = (end - start)/1000000;
    System.out.println("Merge Sort Time:" + duration + "ms");

//QUICK SORT
    long s = System.nanoTime();
    quickSort(arr3, 0, a-1);
    long e = System.nanoTime();
    long d = (e - s);
    System.out.println("Quick Sort Time:" + duration + "ms");
}


public static int[] newArr(int a, int n) {
    Random rand = new Random();
    int newArray[] = new int[a];
     for (int i = 0; i < a; i++) {
         int number= rand.nextInt(n);
         newArray[i]=number;
     }
    return newArray;
}

public static void quickSort(int[] arr, int low, int high) {
    if(low<high) {
        int pivotIndex = findPivot(arr, low, high);
        quickSort(arr, low, pivotIndex-1);
        quickSort(arr, pivotIndex+1, high);
    }
}

public static int findPivot(int[] arr, int low, int high) {
    int pivot = arr[high];
    int nextSmallest = (low-1);
    for(int currentIndex = low; currentIndex < high; currentIndex++) {
        if(arr[currentIndex] <= pivot) {
            nextSmallest++;
            int temp = arr[nextSmallest];
            arr[nextSmallest] = arr[currentIndex];
            arr[currentIndex] = temp;
        }
    }
    int temp = arr[nextSmallest+1];
    arr[nextSmallest+1] = arr[high];
    arr[high] = temp;
    return nextSmallest+1;
}

public static void mergeSort(int[] arr, int left, int right){
    if(left<right) {
        int middle = (left + right) / 2;
        mergeSort(arr, left, middle);
        mergeSort(arr, middle+1, right);
        merge(arr, left, middle, right);
    }
}

public static void merge(int[] arr, int left, int middle, int right){
    int leftLength = middle - left + 1;
    int rightLength = right - middle;
    int newL[] = new int [leftLength];
    int newR[] = new int [rightLength];
    for (int i=0; i<leftLength; ++i)
        newL[i] = arr[left + i];
    for (int j=0; j<rightLength; ++j)
        newR[j] = arr[middle + 1+ j];
    int i = 0, j = 0;
    int k = left;
    while (i < leftLength && j < rightLength) {
        if (newL[i] <= newR[j]) {
            arr[k] = newL[i];
            i++;
        }
        else {
            arr[k] = newR[j];
            j++;
        }
        k++;
    }
    while (i < leftLength) {
        arr[k] = newL[i];
        i++;
        k++;
    }
    while (j < rightLength) {
        arr[k] = newR[j];
        j++;
        k++;
    }
}

static void printArray(int arr[], String methodName) {
        System.out.print(methodName);
    int n = arr.length;
    for (int i=0; i<n; ++i)
        System.out.print(arr[i] + " ");
    System.out.println();
}

public static void insertSort(int[] arr){
    int temp;
    for(int i = 0; i < arr.length; i++) {
        for(int j = i ; j > 0 ; j--){
            if(arr[j] < arr[j-1]){
                temp = arr[j];
                arr[j] = arr[j-1];
                arr[j-1] = temp;
            }
        }
    }
}
}

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