java语言递归求数组中所有元素的总和
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Find the sum of all elements in array recursively in java language
提问by
Here is my code:
这是我的代码：
public int sum(int[] array, int index)
{
//int index is the number of elements in the array.
//Here is my base case:
if (index == 0)
return 0;
//Now it's time for the recursion
else
return array[index] + sum(array, index + 1);
}
I keep on getting an out of bounds error, but I don't what I am doing wrong.
我不断收到越界错误，但我不知道我做错了什么。
回答by Rohit Jain
Your base condition is faulty. It should be:
你的基本条件有问题。它应该是：
if (index == array.length)
Note, you need to pass index = 0on first call. If you are passing index = array.length - 1, then keep the base case as it is, and change the recursive method invocation to pass index - 1, instead of index + 1.
请注意，您需要传递index = 0第一个电话。如果您正在传递index = array.length - 1，则保持基本情况不变，并将递归方法调用更改为 pass index - 1，而不是index + 1。
However, do you really need recursion? I would seriously give it hundreds of thoughts before reaching out for recursion instead of loop for this task.
然而，你真的需要递归吗？在针对此任务进行递归而不是循环之前，我会认真地给它数百个想法。
回答by Masudul
Try,
尝试，
public static void main(String[] args){
int arr[] = {3, 4, 6, 7};
System.out.println(sum(arr, arr.length-1));
}
public static int sum(int[] array, int index) {
if (index == 0) {
return array[0];
} else {
return array[index] + sum(array, index - 1);
}
}
回答by Timothy Do
@ Masud - you're code has a logical error though (i'm beginner Java so sorry if i'm incorrect).
@ Masud - 不过你的代码有一个逻辑错误（我是 Java 初学者，如果我不正确，很抱歉）。
return array[index] + sum(array, index - 1);
array[index]
will receive a out-of-bounds error as index starts at 0 - hence meaning there won't be an index there. 'index - 1' would work. Also, this would change your base case to return '0' as returning array[0] will have array[0] added twice and an incorrect sum.
将收到越界错误，因为索引从 0 开始 - 因此意味着那里不会有索引。'index - 1' 会起作用。此外，这会将您的基本情况更改为返回“0”，因为返回 array[0] 会将 array[0] 添加两次并且总和不正确。
This is my code:
这是我的代码：
public static int sumArrayRecursion(int array[], int n){
if (n == 0){
return 0;
}
else {
return array[n-1] + sumArrayRecursion(array, n-1);
}
}
回答by Sumama Waheed
instead of going from 0 to highest index , go from highest index to 0, i did (index -1) because you said index is total elements, so if array has 10 elements, last element has index 9
而不是从 0 到最高索引，从最高索引到 0，我做了（索引 -1），因为你说索引是总元素，所以如果数组有 10 个元素，最后一个元素的索引为 9
public int sum(int[] array, int index)
{
//int index is the number of elements in the array.
//Here is my base case:
if (index == 0)
return 0;
//Now it's time for the recursion
else
return array[index-1] + sum(array, (index - 1);
}
回答by Theresa Forster
If you are using Java 1.8 you can do the following
如果您使用的是 Java 1.8，您可以执行以下操作
public int sum(int[] array)
{
return (int)array.stream().sum();
}
or even
甚至
public int sum(int[] array)
{
return (int)array.sum();
}
