6-5日

Max Points on a Line

开始无脑匹配结果超时：

class Solution {
public:
    int maxPoints(vector<Point> &points) {
        int ans = 0;
        for (int i = 0; i < points.size(); ++i) {
            for (int j = i + 1; j < points.size(); ++j) {
                int num = 1;
                for (int k = 0; k < points.size(); ++k)
                    if (isOnLine(points[i], points[j], points[k])) num++;
                if (num > ans) ans = num;
            }
        }
        if (ans == 0 && points.size() == 1) ans = 1;
        return ans;
    }
    
    bool isOnLine(const Point &p1, const Point &p2, const Point &p) {
        if ((p.y - p2.y) * (p.x - p1.x) == (p.y - p1.y) * (p.x - p2.x))
            return true;
        return false;
    }
};

统计同一斜率的直线数量：

class Solution {
public:
    int maxPoints(vector<Point> &points) {
        int ans = 0;
        unordered_map<float, int> kmap;
        for (int i = 0; i < points.size(); ++i) {
            kmap.clear();
            int duplicate = 1;
            for (int j = 0; j < points.size(); ++j ) {
                if (j == i) continue;
                if (points[i].x == points[j].x && points[i].y == points[j].y) {
                    ++duplicate;
                    continue;
                }
                float k = (points[i].x == points[j].x) ? INT_MAX : 
                (float)(points[i].y - points[j].y) / (points[i].x - points[j].x);
                kmap[k]++;
            }
            unordered_map<float, int>::iterator it = kmap.begin();
            while (it != kmap.end()) {
                if (it->second + duplicate > ans)
                    ans = it->second + duplicate;
                ++it;
            }
            if (ans < duplicate) ans = duplicate;
        }
        return ans;
    }
};

Sort List

 

class Solution {
public:
    ListNode *sortList(ListNode *head) {
        if (head == NULL || head->next == NULL)
            return head;
        ListNode *slow = head, *fast = head;
        while (fast->next != NULL && fast->next->next != NULL) {
            fast = fast->next->next;
            slow = slow->next;
        }
        fast = slow;
        slow = slow->next;
        fast->next = NULL;
        fast = sortList(head);
        slow = sortList(slow);
        return merge(fast, slow);
    }
    
    ListNode *merge(ListNode *first, ListNode *second) {
        if (first == NULL) return second;
        if (second == NULL) return first;
        ListNode *ret, *p;
        if (first->val < second->val) {
            ret = first;
            first = first->next;
        } else {
            ret = second;
            second = second->next;
        }
        p = ret;
        while (first != NULL && second != NULL) {
            if (first->val <second->val) {
                p->next = first;
                first = first->next;
            } else {
                p->next = second;
                second = second->next;
            }
            p = p->next;
        }
        if (first != NULL) p->next = first;
        else if (second != NULL) p->next = second;
        return ret;
    }

};

Insertion Sort List

class Solution {
public:
    ListNode *insertionSortList(ListNode *head) {
        if (head == NULL || head->next == NULL) return head;
        ListNode *cur = head->next;
        while (cur != NULL) {
            ListNode *p = head;
            while (p->val < cur->val && p != cur) p = p->next;
            while (p != cur) {
                swap(p->val, cur->val);
                p = p->next;
            }
            cur = cur->next;
        }
        return head;
    }
   
};