Question

我试图使用递归打印出与给定总和相等的所有子集。但是，我的代码在完成第一个代码后不会跳转到下一个迭代：

import java.util.*;
public class Combinations {
public static int currentSum = 0;
public static ArrayList<Integer> usedItems = new ArrayList<>();
public static void main( String[] args ) throws Exception {

    int arr[] = {1, 2, 3, 4, 2};
    int sum = 6;
    printCombinations(arr, sum);
}

public static void printCombinations(int[] availableItems, int goal){

    for (int i = 0; i < availableItems.length; i++){
        if (currentSum + availableItems[i] == goal){
            System.out.println(Arrays.toString(usedItems.toArray()) + availableItems[i]);
            currentSum = 0;
            usedItems.clear();
        }
        if(currentSum + availableItems[i] > goal){
            continue;
        }
        if(currentSum + availableItems[i] < goal){
            currentSum += availableItems[i];
            usedItems.add(availableItems[i]);
            int[] newAvailableItems = Arrays.copyOfRange(availableItems, 1, availableItems.length);
            printCombinations(newAvailableItems, goal);
        }
    }
}

例如，如果总和等于6，程序只打印出1,2,3但不跳转到下一个数字并从那里检查。

Answer 1

我认为问题在于：

 if (currentSum + availableItems[i] == goal)

对于给定的数组int arr[] = {1, 2, 3, 4, 2};和目标价值int sum = 6;

迭代：

currentSum = 0, availableItems[i] = 1（0 + 1 = 1）适合 - ＆gt; if(currentSum + availableItems[i] < goal)
currentSum = 1, availableItems[i] = 2（1 + 2 = 3）适合 - ＆gt; if(currentSum + availableItems[i] < goal)
currentSum = 3, availableItems[i] = 3（3 + 3 = 6）适合 - ＆gt; if (currentSum + availableItems[i] == goal)并在同一次迭代中：currentSum = 0, availableItems[i] = 3（0 + 3 = 3）适合 - ＆gt; if (currentSum + availableItems[i] < goal)
currentSum = 3, availableItems[i] = 4（3 + 4 = 7）适合 - ＆gt; if(currentSum + availableItems[i] > goal)等等......

对于给定的数组，sum值不适合第一个，如果不是。

您需要增加迭代器：

if (currentSum + availableItems[i] == goal){
    System.out.println(Arrays.toString(usedItems.toArray()) + availableItems[i]);
    currentSum = 0;
    usedItems.clear();
    i++;
}

打印出一个数组中的所有子集，它们递归地等于给定的和不会跳转到下一次迭代

1 个答案: