leetcode-剑指35-OK

// language C with STL(C++)
// 剑指35
// https://leetcode-cn.com/problems/fu-za-lian-biao-de-fu-zhi-lcof/comments/
// 同主站138
// https://leetcode-cn.com/problems/copy-list-with-random-pointer/

/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* next;
    Node* random;
    
    Node(int _val) {
        val = _val;
        next = NULL;
        random = NULL;
    }
};
*/
class Solution {
	Node* CreatANode(int val){
		Node* ans =(Node *) malloc(sizeof(Node));
		ans->val = val;
		ans->next = NULL;
		ans->random = NULL;
		return ans;
	}
public:
    Node* copyRandomList(Node* head) {
    	if(head == NULL)
    		return NULL;
        // 先把链表的指针都装进一个vector里
        vector<Node*> old;
        Node* p = head;
        while(p){
        	old.push_back(p);
        	p = p -> next;
        }
        int size_old = old.size();


        int random[size_old];
        for(int i = 0 ; i < size_old; i++){
        	p = old[i]->random;
        	if(p == NULL)
        		random[i] = -1;
        	else{
        		for(int j = 0; j<size_old; j++){
        			if(p == old[j])
        				random[i] = j;
        		}
        	}
        }



        Node* ans[size_old];
        ans[size_old-1] = CreatANode(old[size_old-1]->val);
        ans[size_old-1] ->next = NULL;
        for(int i = size_old-2; i>=0; i--){
        	ans[i] = CreatANode(old[i]->val);
        	ans[i]->next = ans[i+1];
        }
        for(int i =0; i<size_old; i++){
        	if(random[i] != -1)
        		ans[i]->random = ans[random[i]];
        }

        return ans[0];
    }
};