如何使用递归嵌套的'for'循环 [英] how to use recursion for nested 'for' loops

问题描述

在java中我有一个嵌套for循环的问题。我的问题是，在一开始我不知道究竟有多少循环，我将需要。它被设置在我的程序的中间。所以说，我的程序创建一个数组。如果数组有3个元素，那么我会创建一个如下所示的三个循环。

  for（int i = 0; i< tab （int k = 0; k< tab [1] .length（）; j ++）{
 for（int k = 0; [2] .length（）; k ++）{
 System.out.println（i ++ j ++ k）; 
 
 
 
 
 
 $如果我的程序创建了一个数组有4个元素，那么它会是这样的：
 
 pre $  for（int i = 0; i< tab [0] .length（ ）;（++）{
 for（int j = 0; j  for（int k = 0; k< tab [2] ）; k ++）{
 for（int h = 0; h  System.out.println（i ++ j ++ k + + H）; 
 
 
 
 
 
 
 
可以任何一个告诉我如何做到这一点与递归？我可以有2个嵌套的循环，但我可以有10个，总是在最后我想打印在与所有循环（i，j，k，h）相关的控制台数字中。
 
解决方案
这是一个解决方案。在每一次递归调用中， previousTabs 变长1， tabs 变短1 
  public static void iterate（int [] previousValues，int [] tabs）{$ b $ if（tabs.length == 0）{
 System .out.println（Arrays.toString（previousValues））; 
} 
 else {
 final int [] values = new int [previousValues.length + 1]; 
 for（int i = 0; i< previousValues.length; i ++）{
 values [i] = previousValues [i]; 
} 
 final int [] nextTabs = new int [tabs.length  -  1]; 
 for（int i = 0; i< nextTabs.length; i ++）{
 nextTabs [i] = tabs [i + 1]; 
} 
 for（int i = 0; i< tabs [0]; i ++）{
 values [values.length-1] = i; 
迭代（values，nextTabs）; 
 
 
 $ b public static void iterate（int [] tabs）{
 iterate（new int [0]，tabs）; 
} 
  
 
I have a problem with nested for loops in java. My problem is that at the beginning I don't know exactly how many for loops I will need. It is set somewhere in the middle of my program. So let say my program creates an array. If the array has 3 elements then I create a three for loops like below.
for(int i = 0; i<tab[0].length() ; i++){
    for(int j = 0; j<tab[1].length() ; j++){
        for(int k = 0; k<tab[2].length() ; k++){
            System.out.println(i+" "+j+" "+k);
        }
    }
}
If my program created an array with 4 elements then it would be like this:
for(int i = 0; i<tab[0].length() ; i++){
    for(int j = 0; j<tab[1].length() ; j++){
        for(int k = 0; k<tab[2].length() ; k++){
             for(int h = 0; h<tab[3].length() ; h++){
                System.out.println(i+" "+j+" "+k+" "+h);
             }
        }
    }
}
Can any one tell me how to do this with recursion? I can have 2 nested loops but I can have 10 of them and always at the end I would like to print in the console numbers associated with all loops (i,j,k,h)
解决方案
Here is a solution. At each recursive call, previousTabs becomes 1 longer and tabs becomes 1 shorter.
public static void iterate(int[] previousValues, int[] tabs) {
    if (tabs.length == 0) {
        System.out.println(Arrays.toString(previousValues));
    }
    else {
        final int[] values = new int[previousValues.length + 1];
        for (int i = 0; i < previousValues.length; i++) {
            values[i] = previousValues[i];
        }
        final int[] nextTabs = new int[tabs.length - 1];
        for (int i = 0; i < nextTabs.length; i++) {
            nextTabs[i] = tabs[i + 1];
        }
        for (int i = 0; i < tabs[0]; i++) {
            values[values.length - 1] = i;
            iterate(values, nextTabs);
        }
    }
}
public static void iterate(int[] tabs) {
    iterate(new int[0], tabs);
}


                        
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