Datawhale-LeetCode编程实践组队学习Task11

136. 只出现一次的数字

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int ans = 0;

        for (int n : nums)
        {
            ans ^= n;
        }

        return ans;
    }
};

141. 环形链表

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    bool hasCycle(ListNode *head) {
        if (head == nullptr || head->next == nullptr)
            return false;
        ListNode *quick, *slow;
        quick = head->next;
        slow = head;

        while (quick != slow)
        {
            if (quick == nullptr || quick->next == nullptr)
                return false;
            quick = quick->next->next;
            slow = slow->next;
        }

        return true;
    }
};

142. 环形链表 II

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *detectCycle(ListNode *head) {
        if (head == nullptr || head->next == nullptr)
            return nullptr;
        ListNode *slow, *quick;
        slow = head;
        quick = head->next;

        while (quick != slow)
        {
            if (quick == nullptr || quick->next == nullptr)
                return nullptr;
            slow = slow->next;
            quick = quick->next->next;
        }

        int cnt = 0;
        do
        {
            quick = quick->next->next;
            slow = slow->next;
            cnt++;
        }while (quick != slow);

        quick = head;
        slow = head;
        while (cnt != 0)
        {
            quick = quick->next;
            cnt--;
        }

        while (quick != slow)
        {
            quick = quick->next;
            slow = slow->next;
        }

        return quick;
    }
};