Careercup

2014-05-01 01:32

题目链接

原题：

Given a linked list where apart from the next pointer, every node also has a pointer named random which can point to any other node in the linked list. Make a copy of the linked list.

题目：给定一个单链表，每个链表除了next指针以外，还有一个random指针，随机地指向nullptr或者链表中的某个节点。请设计算法完成一份链表的硬拷贝。

解法：Leetcode上有相关题目，请看题解LeetCode - Copy List with Random Pointer。

代码：

// http://www.careercup.com/question?id=5412018236424192
#include <unordered_map>
using namespace std;

struct RandomListNode {
    int label;
    RandomListNode *next, *random;
    RandomListNode(int x) : label(x), next(NULL), random(NULL) {};
};

class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int n;
        
        if(nullptr == head){
            return nullptr;
        }
        
        n = 0;
        RandomListNode *ptr;
        
        ptr = head;
        while(ptr != nullptr){
            ++n;
            mri[ptr] = n;
            ptr = ptr->next;
        }
        
        RandomListNode *root, *tail;
        ptr = head;
        
        int i = 0;
        tail = root = nullptr;
        while(ptr != nullptr){
            ++i;
            if (root == nullptr) {
                root = tail = new RandomListNode(ptr->label);
            } else {
                tail->next = new RandomListNode(ptr->label);
                tail = tail->next;
            }
            mir[i] = tail;
            ptr = ptr->next;
        }
        
        RandomListNode *p1, *p2;
        
        p1 = head;
        p2 = root;
        while(p1 != nullptr){
            if(p1->random != nullptr){
                p2->random = mir[mri[p1->random]];
            }
            p1 = p1->next;
            p2 = p2->next;
        }
        
        mir.clear();
        mri.clear();
        
        return root;
    }
private:
    unordered_map<RandomListNode *, int> mri;
    unordered_map<int, RandomListNode *> mir;
};