使用Java中的排序算法 [英] Using a sort algorithm in Java

问题描述

我是想根据我们的编程讲座使用排序算法。也许我只是失去了一些东西。

我会AP preciate，如果有人可以帮助我还是可以给我一个大概的任何错误，我做了提示。

下面我目前的code：

 包Sortieralgorithmus;

公共类排序{

公共静态INT [] straightSelection（INT []号）{

    的for（int i = 0; I＆LT; numbers.length;我++）{
        INT smallestIndex =我;

        对于（INT J = I + 1; J＆LT; numbers.length; J ++）{
            如果（数字[1]  - ;数字[smallestIndex]）{
                smallestIndex = j的;
            }
        }
        掉期（J，I，数字）;


    }

    返回的数字;
}
}
 

解决方案

您正在做的就地选择排序。 更改

 如果（数字[1]  - ;数字[smallestIndex]）
 

到

 如果（号码[J] LT;数字[smallestIndex]）
 

也改变

 （INT I = 0; I＆LT; numbers.length;我++）
 

到

 （INT I = 0; I＆LT; numbers.length（） -  1;我++）
 

此外，由于i和j在你的宣布参加条件，他们只的范围for循环中访问。相反，声明它们的循环之外。

最后，这是一个好主意，检查如果（smallestIndex！= 1）交换之前。

因此，这里是你的工作code ，假设您的交换功能的正常工作。

 包Sortieralgorithmus;

公共类排序{

公共静态INT [] straightSelection（INT []号）{
INT I，J; //这里声明它们
INT smallestIndex; //声明它在这里也

对于（i = 0; I＆LT; numbers.length-1;我++）{
    smallestIndex =我;

    为（J = I + 1; J＆LT; numbers.length; J ++）{
        如果（号码[J] LT;数字[smallestIndex]）{
            smallestIndex = j的;
        }
    }
    如果（smallestIndex！=ⅰ）{
    掉期（smallestIndex，我，号码）;
    }

}

返回的数字;
}
}
 

请参阅以下内容： http://en.wikipedia.org/wiki/Selection_sort

I was trying to use a sort algorithm according to our programming lecture. Maybe I am just missing something.

I would appreciate it if someone may help me out or could give me a hint about any mistake I made.

Here my current code:

package Sortieralgorithmus;

public class sort {

public static int[] straightSelection(int[] numbers) {

    for (int i = 0; i < numbers.length; i++) {
        int smallestIndex = i;

        for (int j = i + 1; j < numbers.length; j++) {
            if (numbers[i] < numbers[smallestIndex]) {
                smallestIndex = j;
            }
        }
        swap(j, i, numbers);


    }

    return numbers;
}
}

解决方案

You are doing an in-place selection sort. Change

if (numbers[i] < numbers[smallestIndex]) 

to

if (numbers[j] < numbers[smallestIndex]) 

Also change

(int i = 0; i < numbers.length; i++)

to

(int i = 0; i < numbers.length()-1; i++)

Additionally, because i and j are declared within your for condition, they are only accessible within the scope of the for loop. Instead, declare them outside of your loops.

Lastly, it's a good idea to check if(smallestIndex != i) before swapping them.

So here's your working code, assuming your swap function works correctly.

package Sortieralgorithmus;

public class sort {

public static int[] straightSelection(int[] numbers) {
int i, j;  // declare them here 
int smallestIndex; //declare it here as well

for (i = 0; i < numbers.length-1; i++) {
    smallestIndex = i;

    for (j = i + 1; j < numbers.length; j++) {
        if (numbers[j] < numbers[smallestIndex]) {
            smallestIndex = j;
        }
    }
    if(smallestIndex != i){
    swap(smallestIndex, i, numbers);
    }

}

return numbers;
}
}

Please refer to the following: http://en.wikipedia.org/wiki/Selection_sort

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