Eclipse一直告诉我我的分区函数有问题。它是用java编写的,是一个关于数组排序的类的一部分。
分区是这样工作的:数组中有两个索引i和j,在分区算法的最开始,i指向数组中的第一个元素,j指向最后一个元素。然后,算法向前移动i,直到找到值大于或等于枢轴的元素。索引j向后移动,直到找到值小于或等于透视的元素。如果i≤j,那么它们被交换,并且i步到下一个位置(i + 1),j步到前一个位置(j - 1)。当i大于j时,算法停止。
你能看到问题出在哪里吗,因为我很难找到它。如果您能帮上忙,我们将不胜感激。
public static int partition(int arr[], int left, int right)
{
int x = arr[right];
int i = left-1;
int temp=0;
for (int j=left; j<right; j++)
{
if(arr[j]<=x)
{
i++;
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
temp = arr[i+1];
arr[i+1] = arr[right];
arr[right] = temp;
return (i+1);
}
编辑
Eclipse说有两个问题,一个是分区函数中的这行代码:
int x = arr[right];
使用我的测试类中的这一行:
sort.partition(array, 100, array.length);
下面是测试类,其中包含我没有提到的函数。
import java.util.Random;
public class test {
/**
* @param args
*/
public static void main(String[] args) {
int size = 1000;
int max = 5000;
int[] array = new int[size];
int loop = 0;
Random generator = new Random();
//Write a loop that generates 1000 integers and
//store them in the array using generator.nextInt(max)
generator.nextInt(max); //generating one
//I need to generate 1000
//So I need some kind of loop that will generate 1000 numbers.
for (int i =0; i<1000; i++)
{
generator.nextInt(max);
}
/**
* After I do this, I'll have the array, array.
* Then comes what's under this.
* THat method is for measuring the time.
* System.currentTimeMillis();,
* with this, I can collect a time for the start of the method
* and one for the end.
* Time at the end, minus the time at the start
* gets us the running time.
*/
long result;
long startTime = System.currentTimeMillis();
sort.quickSort(array, 100, array.length-1);
long endTime = System.currentTimeMillis();
result = endTime-startTime;
System.out.println("The quick sort runtime is " + result + " miliseconds");
long result2;
long startTime2 = System.currentTimeMillis();
sort.partition(array, 100, array.length);
long endTime2 = System.currentTimeMillis();
result2 = endTime2 - startTime2;
System.out.println("The partition runtime is "+result2 + " miliseconds");
long result3;
long startTime3 = System.currentTimeMillis();
sort.bubbleSort(array, 100);
long endTime3 = System.currentTimeMillis();
result3 = endTime3-startTime3;
System.out.println("The bubble sort runtime is "+result3 + " miliseconds");
long result4;
long startTime4 = System.currentTimeMillis();
sort.selectionSort(array, 100); //change the second number to change
//the size of an array.
long endTime4 = System.currentTimeMillis();
result4 = endTime4-startTime4;
System.out.println("The selection sort runtime is "+result4 + " miliseconds");
}
}
发布于 2013-04-25 02:31:06
首先,您实际上并没有在数组中存储随机数,所以它将是全零的。
至于你看到的实际错误,你已经得到了一个错误的经典错误。您有两个选择:让right
指向数组的末尾,或者指向数组的末尾。其中任何一个都是有效的,但是您将这两个混合在一起。
具体地说,您为right
值传递了1000 (超过数组末尾一次),但随后您立即用它对数组进行索引,自然地抛出了异常。
https://stackoverflow.com/questions/16204979
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