203. Remove Linked List Elements

Problem

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Difficulty: Easy
Tags: Linked List, Recursion

Intuition

The first intuition of this problem is that it looked pretty easy. it was like practice problem for “intro to computer Science 101” class.

Approach

it removes the target value nodes.

Solution

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* removeElements(struct ListNode* head, int val) {
    if(!head){return NULL;}
    if(head->val == val){
        return removeElements(head->next, val);
    }
    if(!(head->next)){
        return head;
    }
    struct ListNode* tmp = head;
    struct ListNode* prev;
    while(tmp){
        printf("%d\n",tmp->val);
        if(tmp->val == val){
            prev->next = tmp->next;
        }
        else{
            prev = tmp;
        }
        tmp = tmp->next;
    }
    return head;
}

Complexity

• Time: $O(n)$

• Space: $O(n)$

Thoughts

good ^^