java - 查找数组中出现的重复项数 - Java

Question

我无法解决这个问题。需要找到重复项，我做到了。现在剩下的就是打印重复出现在数组中的次数。我刚开始使用 Java，所以这需要硬编码才能让我理解。花了最后两天试图弄清楚但没有运气..任何帮助都会很棒!话不多说，这里是代码..

import java.util.Arrays;
public class LoopTest {

    public static void main(String[] args) {

        int[] array = {12,23,-22,0,43,545,-4,-55,43,12,0,-999,-87};
        int positive_counter = 0;
        int negative_counter = 0;


        for (int i = 0; i < array.length; i++) {
            if(array[i] > 0) {
                positive_counter++;
            } else if(array[i] < 0) {
                negative_counter++;
            }
        }

        int[] positive_array = new int[positive_counter];
        int[] negative_array = new int[negative_counter];

        positive_counter = 0;
        negative_counter = 0;

        for (int i = 0; i < array.length; i++) {
            if(array[i] > 0) {
                positive_array[positive_counter++] = array[i];
            } else if(array[i] < 0) {
                negative_array[negative_counter++] = array[i];
            }
        }

        System.out.println("Positive array: " + (Arrays.toString(positive_array)));
        System.out.println("Negative array: " + (Arrays.toString(negative_array)));

        Arrays.sort(array);
        System.out.println("Array duplicates: ");
        for (int i = 0; i < array.length; i++) {
            for (int j = i + 1; j < array.length; j++) {
                if(array[i] == array[j]) {                    
                    System.out.println(array[j]);
                }

            }
        }
    }
}

Answer 1

由于您已经对数组进行了排序，因此您只需一个循环即可找到重复项(它们将彼此相邻，对吗？)。所以你可以这样做:

            Arrays.sort(array);
            System.out.println("Array duplicates: ");
            int lastValueCount=1; //How many times we met the current value (at least 1 - this time)
            for (int i = 1; i < array.length; i++){        
                    if(array[i] == array[i-1])                     
                        lastValueCount++;   //If it is the same as the previous increase the count  
                    else {
                       if(lastValueCount>1) //If it is duplicate print it
                           System.out.println(array[i-1]+" was found "+lastValueCount+" times");
                       lastValueCount=1; //reset the counter
                    }
            }

你的数组的结果是:

Array duplicates: 
0 was found 2 times
12 was found 2 times
43 was found 2 times

您也可以使用一些 Java 花里胡哨的东西，比如将值插入 Map 或类似的东西，但我猜您是从算法的角度来看的，所以上面是一个简单的答案，只有一个循环