改组链表Java [英] Shuffling an linked list Java
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问题描述
我很难使用伪代码进行改组算法并将其转换为有效的Java代码.我正在尝试随机播放链接列表.总体而言,该方法采用链接列表的开头的指针,并随机返回指向同一列表的开头的指针.我想使用我创建的getLength和getItem方法.
I'm having a very hard time using a pseudo code for the shuffling algorithm and turning it to a working java code. I'm attempting to shuffle a linked list. Overall the method takes the pointer of the head of the linked list and returns a pointer to the head of the same list randomly. I want to use a getLength and getItem method I've created.
public static ListElement shuffle(ListElement head){
head = head.getLength();
ListElement head2= null;
while( head == null) {
int random = (int) Math.random() * n;
for(int i=0;i<random;i++){
head= head.getNext();
}
}
return head;
}
伪代码:
A list L of length n
A new list R, empty
while L is not empty
pick a random k
such that 0<=k<= (length L)
remove the kth element of L
call it e
prepend e to R
推荐答案
我只是稍微重写一下代码,使其遵循伪代码.
I just rewrite the code a bit so that it follows the pseudo code.
ListElement head2 = null;
int length = head.getLength();
while (head != null) {
int k = (int) Math.random() * length;
// Assume there is function deleteAt(index) that removes
// the element at specified index and returns the deleted
// element
ListElement e = head.deleteAt(k);
// Although I can just give the implementation - I'll leave this
// as exercise.
// You can have a function that add element to front
// head2.addFront(e);
e.setNext(head2);
head2 = e;
// Instead of querying the length again
// decrement the length
length--;
}
return head;
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